diff --git a/extern/filecoin-ffi b/extern/filecoin-ffi
index 5342c7c97..cddc56607 160000
--- a/extern/filecoin-ffi
+++ b/extern/filecoin-ffi
@@ -1 +1 @@
-Subproject commit 5342c7c97d1a1df4650629d14f2823d52889edd9
+Subproject commit cddc56607e1d851ea6d09d49404bd7db70cb3c2e
diff --git a/faults.go b/faults.go
index 8580c0d93..ea0ab6e01 100644
--- a/faults.go
+++ b/faults.go
@@ -43,9 +43,11 @@ func (m *Manager) CheckProvable(ctx context.Context, spt abi.RegisteredSealProof
 				return nil
 			}
 
-			lp, _, err := m.localStore.AcquireSector(ctx, sector, spt, stores.FTSealed|stores.FTCache, stores.FTNone, false, stores.AcquireMove)
+			lp, _, err := m.localStore.AcquireSector(ctx, sector, spt, stores.FTSealed|stores.FTCache, stores.FTNone, stores.PathStorage, stores.AcquireMove)
 			if err != nil {
-				return xerrors.Errorf("acquire sector in checkProvable: %w", err)
+				log.Warnw("CheckProvable Sector FAULT: acquire sector in checkProvable", "sector", sector, "error", err)
+				bad = append(bad, sector)
+				return nil
 			}
 
 			if lp.Sealed == "" || lp.Cache == "" {
diff --git a/ffiwrapper/partialfile.go b/ffiwrapper/partialfile.go
index a2c1f1151..3e8b32288 100644
--- a/ffiwrapper/partialfile.go
+++ b/ffiwrapper/partialfile.go
@@ -12,6 +12,7 @@ import (
 	rlepluslazy "github.com/filecoin-project/go-bitfield/rle"
 	"github.com/filecoin-project/specs-actors/actors/abi"
 
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"github.com/filecoin-project/sector-storage/storiface"
 )
 
@@ -144,10 +145,15 @@ func openPartialFile(maxPieceSize abi.PaddedPieceSize, path string) (*partialFil
 			return xerrors.Errorf("getting trailer run iterator: %w", err)
 		}
 
-		lastSet, err := rlepluslazy.LastIndex(it, true)
+		f, err := rlepluslazy.Fill(it)
+		if err != nil {
+			return xerrors.Errorf("filling bitfield: %w", err)
+		}
+		lastSet, err := rlepluslazy.Count(f)
 		if err != nil {
 			return xerrors.Errorf("finding last set byte index: %w", err)
 		}
+
 		if lastSet > uint64(maxPieceSize) {
 			return xerrors.Errorf("last set byte at index higher than sector size: %d > %d", lastSet, maxPieceSize)
 		}
@@ -218,6 +224,28 @@ func (pf *partialFile) MarkAllocated(offset storiface.PaddedByteIndex, size abi.
 	return nil
 }
 
+func (pf *partialFile) Free(offset storiface.PaddedByteIndex, size abi.PaddedPieceSize) error {
+	have, err := pf.allocated.RunIterator()
+	if err != nil {
+		return err
+	}
+
+	if err := fsutil.Deallocate(pf.file, int64(offset), int64(size)); err != nil {
+		return xerrors.Errorf("deallocating: %w", err)
+	}
+
+	s, err := rlepluslazy.Subtract(have, pieceRun(offset, size))
+	if err != nil {
+		return err
+	}
+
+	if err := writeTrailer(int64(pf.maxPiece), pf.file, s); err != nil {
+		return xerrors.Errorf("writing trailer: %w", err)
+	}
+
+	return nil
+}
+
 func (pf *partialFile) Reader(offset storiface.PaddedByteIndex, size abi.PaddedPieceSize) (*os.File, error) {
 	if _, err := pf.file.Seek(int64(offset), io.SeekStart); err != nil {
 		return nil, xerrors.Errorf("seek piece start: %w", err)
@@ -251,6 +279,25 @@ func (pf *partialFile) Allocated() (rlepluslazy.RunIterator, error) {
 	return pf.allocated.RunIterator()
 }
 
+func (pf *partialFile) HasAllocated(offset storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) (bool, error) {
+	have, err := pf.Allocated()
+	if err != nil {
+		return false, err
+	}
+
+	u, err := rlepluslazy.And(have, pieceRun(offset.Padded(), size.Padded()))
+	if err != nil {
+		return false, err
+	}
+
+	uc, err := rlepluslazy.Count(u)
+	if err != nil {
+		return false, err
+	}
+
+	return abi.PaddedPieceSize(uc) == size.Padded(), nil
+}
+
 func pieceRun(offset storiface.PaddedByteIndex, size abi.PaddedPieceSize) rlepluslazy.RunIterator {
 	var runs []rlepluslazy.Run
 	if offset > 0 {
diff --git a/ffiwrapper/sealer_cgo.go b/ffiwrapper/sealer_cgo.go
index 6510f81cc..8a4f18bc7 100644
--- a/ffiwrapper/sealer_cgo.go
+++ b/ffiwrapper/sealer_cgo.go
@@ -15,6 +15,7 @@ import (
 	"golang.org/x/xerrors"
 
 	ffi "github.com/filecoin-project/filecoin-ffi"
+	rlepluslazy "github.com/filecoin-project/go-bitfield/rle"
 	commcid "github.com/filecoin-project/go-fil-commcid"
 	"github.com/filecoin-project/specs-actors/actors/abi"
 	"github.com/filecoin-project/specs-storage/storage"
@@ -81,7 +82,7 @@ func (sb *Sealer) AddPiece(ctx context.Context, sector abi.SectorID, existingPie
 
 	var stagedPath stores.SectorPaths
 	if len(existingPieceSizes) == 0 {
-		stagedPath, done, err = sb.sectors.AcquireSector(ctx, sector, 0, stores.FTUnsealed, true)
+		stagedPath, done, err = sb.sectors.AcquireSector(ctx, sector, 0, stores.FTUnsealed, stores.PathSealing)
 		if err != nil {
 			return abi.PieceInfo{}, xerrors.Errorf("acquire unsealed sector: %w", err)
 		}
@@ -91,7 +92,7 @@ func (sb *Sealer) AddPiece(ctx context.Context, sector abi.SectorID, existingPie
 			return abi.PieceInfo{}, xerrors.Errorf("creating unsealed sector file: %w", err)
 		}
 	} else {
-		stagedPath, done, err = sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, 0, true)
+		stagedPath, done, err = sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, 0, stores.PathSealing)
 		if err != nil {
 			return abi.PieceInfo{}, xerrors.Errorf("acquire unsealed sector: %w", err)
 		}
@@ -167,14 +168,14 @@ func (sb *Sealer) AddPiece(ctx context.Context, sector abi.SectorID, existingPie
 		return abi.PieceInfo{}, xerrors.Errorf("generate unsealed CID: %w", err)
 	}
 
-	commp, err := commcid.CIDToDataCommitmentV1(pieceCID)
-	if err != nil {
+	// validate that the pieceCID was properly formed
+	if _, err := commcid.CIDToPieceCommitmentV1(pieceCID); err != nil {
 		return abi.PieceInfo{}, err
 	}
 
 	return abi.PieceInfo{
 		Size:     pieceSize.Padded(),
-		PieceCID: commcid.PieceCommitmentV1ToCID(commp),
+		PieceCID: pieceCID,
 	}, nil
 }
 
@@ -198,12 +199,12 @@ func (sb *Sealer) UnsealPiece(ctx context.Context, sector abi.SectorID, offset s
 	maxPieceSize := abi.PaddedPieceSize(sb.ssize)
 
 	// try finding existing
-	unsealedPath, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, stores.FTNone, false)
+	unsealedPath, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, stores.FTNone, stores.PathStorage)
 	var pf *partialFile
 
 	switch {
 	case xerrors.Is(err, storiface.ErrSectorNotFound):
-		unsealedPath, done, err = sb.sectors.AcquireSector(ctx, sector, stores.FTNone, stores.FTUnsealed, false)
+		unsealedPath, done, err = sb.sectors.AcquireSector(ctx, sector, stores.FTNone, stores.FTUnsealed, stores.PathStorage)
 		if err != nil {
 			return xerrors.Errorf("acquire unsealed sector path (allocate): %w", err)
 		}
@@ -240,7 +241,7 @@ func (sb *Sealer) UnsealPiece(ctx context.Context, sector abi.SectorID, offset s
 		return nil
 	}
 
-	srcPaths, srcDone, err := sb.sectors.AcquireSector(ctx, sector, stores.FTCache|stores.FTSealed, stores.FTNone, false)
+	srcPaths, srcDone, err := sb.sectors.AcquireSector(ctx, sector, stores.FTCache|stores.FTSealed, stores.FTNone, stores.PathStorage)
 	if err != nil {
 		return xerrors.Errorf("acquire sealed sector paths: %w", err)
 	}
@@ -253,7 +254,10 @@ func (sb *Sealer) UnsealPiece(ctx context.Context, sector abi.SectorID, offset s
 	defer sealed.Close()
 
 	var at, nextat abi.PaddedPieceSize
-	for {
+	first := true
+	for first || toUnseal.HasNext() {
+		first = false
+
 		piece, err := toUnseal.NextRun()
 		if err != nil {
 			return xerrors.Errorf("getting next range to unseal: %w", err)
@@ -357,10 +361,10 @@ func (sb *Sealer) UnsealPiece(ctx context.Context, sector abi.SectorID, offset s
 	return nil
 }
 
-func (sb *Sealer) ReadPiece(ctx context.Context, writer io.Writer, sector abi.SectorID, offset storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) error {
-	path, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, stores.FTNone, false)
+func (sb *Sealer) ReadPiece(ctx context.Context, writer io.Writer, sector abi.SectorID, offset storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) (bool, error) {
+	path, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, stores.FTNone, stores.PathStorage)
 	if err != nil {
-		return xerrors.Errorf("acquire unsealed sector path: %w", err)
+		return false, xerrors.Errorf("acquire unsealed sector path: %w", err)
 	}
 	defer done()
 
@@ -368,34 +372,45 @@ func (sb *Sealer) ReadPiece(ctx context.Context, writer io.Writer, sector abi.Se
 
 	pf, err := openPartialFile(maxPieceSize, path.Unsealed)
 	if xerrors.Is(err, os.ErrNotExist) {
-		return xerrors.Errorf("opening partial file: %w", err)
+		return false, xerrors.Errorf("opening partial file: %w", err)
+	}
+
+	ok, err := pf.HasAllocated(offset, size)
+	if err != nil {
+		pf.Close()
+		return false, err
+	}
+
+	if !ok {
+		pf.Close()
+		return false, nil
 	}
 
 	f, err := pf.Reader(offset.Padded(), size.Padded())
 	if err != nil {
 		pf.Close()
-		return xerrors.Errorf("getting partial file reader: %w", err)
+		return false, xerrors.Errorf("getting partial file reader: %w", err)
 	}
 
 	upr, err := fr32.NewUnpadReader(f, size.Padded())
 	if err != nil {
-		return xerrors.Errorf("creating unpadded reader: %w", err)
+		return false, xerrors.Errorf("creating unpadded reader: %w", err)
 	}
 
 	if _, err := io.CopyN(writer, upr, int64(size)); err != nil {
 		pf.Close()
-		return xerrors.Errorf("reading unsealed file: %w", err)
+		return false, xerrors.Errorf("reading unsealed file: %w", err)
 	}
 
 	if err := pf.Close(); err != nil {
-		return xerrors.Errorf("closing partial file: %w", err)
+		return false, xerrors.Errorf("closing partial file: %w", err)
 	}
 
-	return nil
+	return false, nil
 }
 
 func (sb *Sealer) SealPreCommit1(ctx context.Context, sector abi.SectorID, ticket abi.SealRandomness, pieces []abi.PieceInfo) (out storage.PreCommit1Out, err error) {
-	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, stores.FTSealed|stores.FTCache, true)
+	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, stores.FTSealed|stores.FTCache, stores.PathSealing)
 	if err != nil {
 		return nil, xerrors.Errorf("acquiring sector paths: %w", err)
 	}
@@ -452,7 +467,7 @@ func (sb *Sealer) SealPreCommit1(ctx context.Context, sector abi.SectorID, ticke
 }
 
 func (sb *Sealer) SealPreCommit2(ctx context.Context, sector abi.SectorID, phase1Out storage.PreCommit1Out) (storage.SectorCids, error) {
-	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTSealed|stores.FTCache, 0, true)
+	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTSealed|stores.FTCache, 0, stores.PathSealing)
 	if err != nil {
 		return storage.SectorCids{}, xerrors.Errorf("acquiring sector paths: %w", err)
 	}
@@ -470,7 +485,7 @@ func (sb *Sealer) SealPreCommit2(ctx context.Context, sector abi.SectorID, phase
 }
 
 func (sb *Sealer) SealCommit1(ctx context.Context, sector abi.SectorID, ticket abi.SealRandomness, seed abi.InteractiveSealRandomness, pieces []abi.PieceInfo, cids storage.SectorCids) (storage.Commit1Out, error) {
-	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTSealed|stores.FTCache, 0, true)
+	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTSealed|stores.FTCache, 0, stores.PathSealing)
 	if err != nil {
 		return nil, xerrors.Errorf("acquire sector paths: %w", err)
 	}
@@ -502,10 +517,62 @@ func (sb *Sealer) SealCommit2(ctx context.Context, sector abi.SectorID, phase1Ou
 
 func (sb *Sealer) FinalizeSector(ctx context.Context, sector abi.SectorID, keepUnsealed []storage.Range) error {
 	if len(keepUnsealed) > 0 {
-		return xerrors.Errorf("keepUnsealed unsupported") // TODO: impl for fastretrieval copies
+		maxPieceSize := abi.PaddedPieceSize(sb.ssize)
+
+		sr := pieceRun(0, maxPieceSize)
+
+		for _, s := range keepUnsealed {
+			si := &rlepluslazy.RunSliceIterator{}
+			if s.Offset != 0 {
+				si.Runs = append(si.Runs, rlepluslazy.Run{Val: false, Len: uint64(s.Offset)})
+			}
+			si.Runs = append(si.Runs, rlepluslazy.Run{Val: true, Len: uint64(s.Size)})
+
+			var err error
+			sr, err = rlepluslazy.Subtract(sr, si)
+			if err != nil {
+				return err
+			}
+		}
+
+		paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTUnsealed, 0, stores.PathStorage)
+		if err != nil {
+			return xerrors.Errorf("acquiring sector cache path: %w", err)
+		}
+		defer done()
+
+		pf, err := openPartialFile(maxPieceSize, paths.Unsealed)
+		if xerrors.Is(err, os.ErrNotExist) {
+			return xerrors.Errorf("opening partial file: %w", err)
+		}
+
+		var at uint64
+		for sr.HasNext() {
+			r, err := sr.NextRun()
+			if err != nil {
+				_ = pf.Close()
+				return err
+			}
+
+			offset := at
+			at += r.Len
+			if !r.Val {
+				continue
+			}
+
+			err = pf.Free(storiface.PaddedByteIndex(abi.UnpaddedPieceSize(offset).Padded()), abi.UnpaddedPieceSize(r.Len).Padded())
+			if err != nil {
+				_ = pf.Close()
+				return xerrors.Errorf("free partial file range: %w", err)
+			}
+		}
+
+		if err := pf.Close(); err != nil {
+			return err
+		}
 	}
 
-	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTCache, 0, false)
+	paths, done, err := sb.sectors.AcquireSector(ctx, sector, stores.FTCache, 0, stores.PathStorage)
 	if err != nil {
 		return xerrors.Errorf("acquiring sector cache path: %w", err)
 	}
@@ -542,33 +609,65 @@ func GeneratePieceCIDFromFile(proofType abi.RegisteredSealProof, piece io.Reader
 	return pieceCID, werr()
 }
 
-func GenerateUnsealedCID(proofType abi.RegisteredSealProof, pieces []abi.PieceInfo) (cid.Cid, error) {
+func GetRequiredPadding(oldLength abi.PaddedPieceSize, newPieceLength abi.PaddedPieceSize) ([]abi.PaddedPieceSize, abi.PaddedPieceSize) {
+
+	padPieces := make([]abi.PaddedPieceSize, 0)
+
+	toFill := uint64(-oldLength % newPieceLength)
+
+	n := bits.OnesCount64(toFill)
 	var sum abi.PaddedPieceSize
-	for _, p := range pieces {
-		sum += p.Size
+	for i := 0; i < n; i++ {
+		next := bits.TrailingZeros64(toFill)
+		psize := uint64(1) << uint(next)
+		toFill ^= psize
+
+		padded := abi.PaddedPieceSize(psize)
+		padPieces = append(padPieces, padded)
+		sum += padded
 	}
 
+	return padPieces, sum
+}
+
+func GenerateUnsealedCID(proofType abi.RegisteredSealProof, pieces []abi.PieceInfo) (cid.Cid, error) {
 	ssize, err := proofType.SectorSize()
 	if err != nil {
 		return cid.Undef, err
 	}
 
-	{
-		// pad remaining space with 0 CommPs
-		toFill := uint64(abi.PaddedPieceSize(ssize) - sum)
-		n := bits.OnesCount64(toFill)
-		for i := 0; i < n; i++ {
-			next := bits.TrailingZeros64(toFill)
-			psize := uint64(1) << uint(next)
-			toFill ^= psize
+	pssize := abi.PaddedPieceSize(ssize)
+	allPieces := make([]abi.PieceInfo, 0, len(pieces))
+	if len(pieces) == 0 {
+		allPieces = append(allPieces, abi.PieceInfo{
+			Size:     pssize,
+			PieceCID: zerocomm.ZeroPieceCommitment(pssize.Unpadded()),
+		})
+	} else {
+		var sum abi.PaddedPieceSize
 
-			unpadded := abi.PaddedPieceSize(psize).Unpadded()
-			pieces = append(pieces, abi.PieceInfo{
-				Size:     unpadded.Padded(),
-				PieceCID: zerocomm.ZeroPieceCommitment(unpadded),
-			})
+		padTo := func(pads []abi.PaddedPieceSize) {
+			for _, p := range pads {
+				allPieces = append(allPieces, abi.PieceInfo{
+					Size:     p,
+					PieceCID: zerocomm.ZeroPieceCommitment(p.Unpadded()),
+				})
+
+				sum += p
+			}
 		}
+
+		for _, p := range pieces {
+			ps, _ := GetRequiredPadding(sum, p.Size)
+			padTo(ps)
+
+			allPieces = append(allPieces, p)
+			sum += p.Size
+		}
+
+		ps, _ := GetRequiredPadding(sum, pssize)
+		padTo(ps)
 	}
 
-	return ffi.GenerateUnsealedCID(proofType, pieces)
+	return ffi.GenerateUnsealedCID(proofType, allPieces)
 }
diff --git a/ffiwrapper/sealer_test.go b/ffiwrapper/sealer_test.go
index 5b3305460..f795be159 100644
--- a/ffiwrapper/sealer_test.go
+++ b/ffiwrapper/sealer_test.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"github.com/ipfs/go-cid"
 	"io"
 	"io/ioutil"
 	"math/rand"
@@ -110,7 +111,7 @@ func (s *seal) unseal(t *testing.T, sb *Sealer, sp *basicfs.Provider, si abi.Sec
 	defer done()
 
 	var b bytes.Buffer
-	err := sb.ReadPiece(context.TODO(), &b, si, 0, 1016)
+	_, err := sb.ReadPiece(context.TODO(), &b, si, 0, 1016)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -120,7 +121,7 @@ func (s *seal) unseal(t *testing.T, sb *Sealer, sp *basicfs.Provider, si abi.Sec
 		t.Fatal("read wrong bytes")
 	}
 
-	p, sd, err := sp.AcquireSector(context.TODO(), si, stores.FTUnsealed, stores.FTNone, false)
+	p, sd, err := sp.AcquireSector(context.TODO(), si, stores.FTUnsealed, stores.FTNone, stores.PathStorage)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -129,7 +130,7 @@ func (s *seal) unseal(t *testing.T, sb *Sealer, sp *basicfs.Provider, si abi.Sec
 	}
 	sd()
 
-	err = sb.ReadPiece(context.TODO(), &b, si, 0, 1016)
+	_, err = sb.ReadPiece(context.TODO(), &b, si, 0, 1016)
 	if err == nil {
 		t.Fatal("HOW?!")
 	}
@@ -140,7 +141,7 @@ func (s *seal) unseal(t *testing.T, sb *Sealer, sp *basicfs.Provider, si abi.Sec
 	}
 
 	b.Reset()
-	err = sb.ReadPiece(context.TODO(), &b, si, 0, 1016)
+	_, err = sb.ReadPiece(context.TODO(), &b, si, 0, 1016)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -149,14 +150,17 @@ func (s *seal) unseal(t *testing.T, sb *Sealer, sp *basicfs.Provider, si abi.Sec
 	require.Equal(t, expect, b.Bytes())
 
 	b.Reset()
-	err = sb.ReadPiece(context.TODO(), &b, si, 0, 2032)
+	have, err := sb.ReadPiece(context.TODO(), &b, si, 0, 2032)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	expect = append(expect, bytes.Repeat([]byte{0}, 1016)...)
-	if !bytes.Equal(b.Bytes(), expect) {
-		t.Fatal("read wrong bytes")
+	if have {
+		t.Errorf("didn't expect to read things")
+	}
+
+	if b.Len() != 0 {
+		t.Fatal("read bytes")
 	}
 }
 
@@ -488,3 +492,105 @@ func requireFDsClosed(t *testing.T, start int) {
 	log.Infow("open FDs", "start", start, "now", openNow)
 	require.Equal(t, start, openNow, "FDs shouldn't leak")
 }
+
+func TestGenerateUnsealedCID(t *testing.T) {
+	pt := abi.RegisteredSealProof_StackedDrg2KiBV1
+	ups := int(abi.PaddedPieceSize(2048).Unpadded())
+
+	commP := func(b []byte) cid.Cid {
+		pf, werr, err := ToReadableFile(bytes.NewReader(b), int64(len(b)))
+		require.NoError(t, err)
+
+		c, err := ffi.GeneratePieceCIDFromFile(pt, pf, abi.UnpaddedPieceSize(len(b)))
+		require.NoError(t, err)
+
+		require.NoError(t, werr())
+
+		return c
+	}
+
+	testCommEq := func(name string, in [][]byte, expect [][]byte) {
+		t.Run(name, func(t *testing.T) {
+			upi := make([]abi.PieceInfo, len(in))
+			for i, b := range in {
+				upi[i] = abi.PieceInfo{
+					Size:     abi.UnpaddedPieceSize(len(b)).Padded(),
+					PieceCID: commP(b),
+				}
+			}
+
+			sectorPi := []abi.PieceInfo{
+				{
+					Size:     2048,
+					PieceCID: commP(bytes.Join(expect, nil)),
+				},
+			}
+
+			expectCid, err := GenerateUnsealedCID(pt, sectorPi)
+			require.NoError(t, err)
+
+			actualCid, err := GenerateUnsealedCID(pt, upi)
+			require.NoError(t, err)
+
+			require.Equal(t, expectCid, actualCid)
+		})
+	}
+
+	barr := func(b byte, den int) []byte {
+		return bytes.Repeat([]byte{b}, ups/den)
+	}
+
+	// 0000
+	testCommEq("zero",
+		nil,
+		[][]byte{barr(0, 1)},
+	)
+
+	// 1111
+	testCommEq("one",
+		[][]byte{barr(1, 1)},
+		[][]byte{barr(1, 1)},
+	)
+
+	// 11 00
+	testCommEq("one|2",
+		[][]byte{barr(1, 2)},
+		[][]byte{barr(1, 2), barr(0, 2)},
+	)
+
+	// 1 0 00
+	testCommEq("one|4",
+		[][]byte{barr(1, 4)},
+		[][]byte{barr(1, 4), barr(0, 4), barr(0, 2)},
+	)
+
+	// 11 2 0
+	testCommEq("one|2-two|4",
+		[][]byte{barr(1, 2), barr(2, 4)},
+		[][]byte{barr(1, 2), barr(2, 4), barr(0, 4)},
+	)
+
+	// 1 0 22
+	testCommEq("one|4-two|2",
+		[][]byte{barr(1, 4), barr(2, 2)},
+		[][]byte{barr(1, 4), barr(0, 4), barr(2, 2)},
+	)
+
+	// 1 0 22 0000
+	testCommEq("one|8-two|4",
+		[][]byte{barr(1, 8), barr(2, 4)},
+		[][]byte{barr(1, 8), barr(0, 8), barr(2, 4), barr(0, 2)},
+	)
+
+	// 11 2 0 0000
+	testCommEq("one|4-two|8",
+		[][]byte{barr(1, 4), barr(2, 8)},
+		[][]byte{barr(1, 4), barr(2, 8), barr(0, 8), barr(0, 2)},
+	)
+
+	// 1 0 22 3 0 00 4444 5 0 00
+	testCommEq("one|16-two|8-three|16-four|4-five|16",
+		[][]byte{barr(1, 16), barr(2, 8), barr(3, 16), barr(4, 4), barr(5, 16)},
+		[][]byte{barr(1, 16), barr(0, 16), barr(2, 8), barr(3, 16), barr(0, 16), barr(0, 8), barr(4, 4), barr(5, 16), barr(0, 16), barr(0, 8)},
+	)
+}
diff --git a/ffiwrapper/types.go b/ffiwrapper/types.go
index 13c0ee990..bc3c44f54 100644
--- a/ffiwrapper/types.go
+++ b/ffiwrapper/types.go
@@ -29,7 +29,7 @@ type Storage interface {
 	StorageSealer
 
 	UnsealPiece(ctx context.Context, sector abi.SectorID, offset storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize, randomness abi.SealRandomness, commd cid.Cid) error
-	ReadPiece(ctx context.Context, writer io.Writer, sector abi.SectorID, offset storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) error
+	ReadPiece(ctx context.Context, writer io.Writer, sector abi.SectorID, offset storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) (bool, error)
 }
 
 type Verifier interface {
diff --git a/ffiwrapper/verifier_cgo.go b/ffiwrapper/verifier_cgo.go
index e3e8dd886..1fecf9598 100644
--- a/ffiwrapper/verifier_cgo.go
+++ b/ffiwrapper/verifier_cgo.go
@@ -15,7 +15,7 @@ import (
 )
 
 func (sb *Sealer) GenerateWinningPoSt(ctx context.Context, minerID abi.ActorID, sectorInfo []abi.SectorInfo, randomness abi.PoStRandomness) ([]abi.PoStProof, error) {
-	randomness[31] = 0                                                                                                                       // TODO: Not correct, fixme
+	randomness[31] &= 0x3f
 	privsectors, skipped, done, err := sb.pubSectorToPriv(ctx, minerID, sectorInfo, nil, abi.RegisteredSealProof.RegisteredWinningPoStProof) // TODO: FAULTS?
 	if err != nil {
 		return nil, err
@@ -29,7 +29,7 @@ func (sb *Sealer) GenerateWinningPoSt(ctx context.Context, minerID abi.ActorID,
 }
 
 func (sb *Sealer) GenerateWindowPoSt(ctx context.Context, minerID abi.ActorID, sectorInfo []abi.SectorInfo, randomness abi.PoStRandomness) ([]abi.PoStProof, []abi.SectorID, error) {
-	randomness[31] = 0 // TODO: Not correct, fixme
+	randomness[31] &= 0x3f
 	privsectors, skipped, done, err := sb.pubSectorToPriv(ctx, minerID, sectorInfo, nil, abi.RegisteredSealProof.RegisteredWindowPoStProof)
 	if err != nil {
 		return nil, nil, xerrors.Errorf("gathering sector info: %w", err)
@@ -62,7 +62,7 @@ func (sb *Sealer) pubSectorToPriv(ctx context.Context, mid abi.ActorID, sectorIn
 
 		sid := abi.SectorID{Miner: mid, Number: s.SectorNumber}
 
-		paths, d, err := sb.sectors.AcquireSector(ctx, sid, stores.FTCache|stores.FTSealed, 0, false)
+		paths, d, err := sb.sectors.AcquireSector(ctx, sid, stores.FTCache|stores.FTSealed, 0, stores.PathStorage)
 		if err != nil {
 			log.Warnw("failed to acquire sector, skipping", "sector", sid, "error", err)
 			skipped = append(skipped, sid)
@@ -98,7 +98,7 @@ func (proofVerifier) VerifySeal(info abi.SealVerifyInfo) (bool, error) {
 }
 
 func (proofVerifier) VerifyWinningPoSt(ctx context.Context, info abi.WinningPoStVerifyInfo) (bool, error) {
-	info.Randomness[31] = 0 // TODO: Not correct, fixme
+	info.Randomness[31] &= 0x3f
 	_, span := trace.StartSpan(ctx, "VerifyWinningPoSt")
 	defer span.End()
 
@@ -106,7 +106,7 @@ func (proofVerifier) VerifyWinningPoSt(ctx context.Context, info abi.WinningPoSt
 }
 
 func (proofVerifier) VerifyWindowPoSt(ctx context.Context, info abi.WindowPoStVerifyInfo) (bool, error) {
-	info.Randomness[31] = 0 // TODO: Not correct, fixme
+	info.Randomness[31] &= 0x3f
 	_, span := trace.StartSpan(ctx, "VerifyWindowPoSt")
 	defer span.End()
 
@@ -114,6 +114,6 @@ func (proofVerifier) VerifyWindowPoSt(ctx context.Context, info abi.WindowPoStVe
 }
 
 func (proofVerifier) GenerateWinningPoStSectorChallenge(ctx context.Context, proofType abi.RegisteredPoStProof, minerID abi.ActorID, randomness abi.PoStRandomness, eligibleSectorCount uint64) ([]uint64, error) {
-	randomness[31] = 0 // TODO: Not correct, fixme
+	randomness[31] &= 0x3f
 	return ffi.GenerateWinningPoStSectorChallenge(proofType, minerID, randomness, eligibleSectorCount)
 }
diff --git a/fsutil/dealloc_linux.go b/fsutil/dealloc_linux.go
new file mode 100644
index 000000000..0b20c568d
--- /dev/null
+++ b/fsutil/dealloc_linux.go
@@ -0,0 +1,28 @@
+package fsutil
+
+import (
+	"os"
+	"syscall"
+
+	logging "github.com/ipfs/go-log/v2"
+)
+
+var log = logging.Logger("fsutil")
+
+const FallocFlPunchHole = 0x02 // linux/falloc.h
+
+func Deallocate(file *os.File, offset int64, length int64) error {
+	if length == 0 {
+		return nil
+	}
+
+	err := syscall.Fallocate(int(file.Fd()), FallocFlPunchHole, offset, length)
+	if errno, ok := err.(syscall.Errno); ok {
+		if errno == syscall.EOPNOTSUPP || errno == syscall.ENOSYS {
+			log.Warnf("could not deallocate space, ignoring: %v", errno)
+			err = nil // log and ignore
+		}
+	}
+
+	return err
+}
diff --git a/fsutil/dealloc_other.go b/fsutil/dealloc_other.go
new file mode 100644
index 000000000..4f8347951
--- /dev/null
+++ b/fsutil/dealloc_other.go
@@ -0,0 +1,17 @@
+// +build !linux
+
+package fsutil
+
+import (
+	"os"
+
+	logging "github.com/ipfs/go-log/v2"
+)
+
+var log = logging.Logger("fsutil")
+
+func Deallocate(file *os.File, offset int64, length int64) error {
+	log.Warnf("deallocating space not supported")
+
+	return nil
+}
diff --git a/fsutil/filesize_unix.go b/fsutil/filesize_unix.go
new file mode 100644
index 000000000..dacdcd515
--- /dev/null
+++ b/fsutil/filesize_unix.go
@@ -0,0 +1,29 @@
+package fsutil
+
+import (
+	"os"
+	"syscall"
+
+	"golang.org/x/xerrors"
+)
+
+type SizeInfo struct {
+	OnDisk int64
+}
+
+// FileSize returns bytes used by a file on disk
+func FileSize(path string) (SizeInfo, error) {
+	var stat syscall.Stat_t
+	if err := syscall.Stat(path, &stat); err != nil {
+		if err == syscall.ENOENT {
+			return SizeInfo{}, os.ErrNotExist
+		}
+		return SizeInfo{}, xerrors.Errorf("stat: %w", err)
+	}
+
+	// NOTE: stat.Blocks is in 512B blocks, NOT in stat.Blksize
+	//  See https://www.gnu.org/software/libc/manual/html_node/Attribute-Meanings.html
+	return SizeInfo{
+		int64(stat.Blocks) * 512, // NOTE: int64 cast is needed on osx
+	}, nil
+}
diff --git a/fsutil/statfs.go b/fsutil/statfs.go
new file mode 100644
index 000000000..2a00ccb9a
--- /dev/null
+++ b/fsutil/statfs.go
@@ -0,0 +1,7 @@
+package fsutil
+
+type FsStat struct {
+	Capacity  int64
+	Available int64 // Available to use for sector storage
+	Reserved  int64
+}
diff --git a/fsutil/statfs_unix.go b/fsutil/statfs_unix.go
new file mode 100644
index 000000000..7fcb8af37
--- /dev/null
+++ b/fsutil/statfs_unix.go
@@ -0,0 +1,19 @@
+package fsutil
+
+import (
+	"syscall"
+
+	"golang.org/x/xerrors"
+)
+
+func Statfs(path string) (FsStat, error) {
+	var stat syscall.Statfs_t
+	if err := syscall.Statfs(path, &stat); err != nil {
+		return FsStat{}, xerrors.Errorf("statfs: %w", err)
+	}
+
+	return FsStat{
+		Capacity:  int64(stat.Blocks) * int64(stat.Bsize),
+		Available: int64(stat.Bavail) * int64(stat.Bsize),
+	}, nil
+}
diff --git a/fsutil/statfs_windows.go b/fsutil/statfs_windows.go
new file mode 100644
index 000000000..d78565182
--- /dev/null
+++ b/fsutil/statfs_windows.go
@@ -0,0 +1,28 @@
+package fsutil
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func Statfs(volumePath string) (FsStat, error) {
+	// From https://github.com/ricochet2200/go-disk-usage/blob/master/du/diskusage_windows.go
+
+	h := syscall.MustLoadDLL("kernel32.dll")
+	c := h.MustFindProc("GetDiskFreeSpaceExW")
+
+	var freeBytes int64
+	var totalBytes int64
+	var availBytes int64
+
+	c.Call(
+		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(volumePath))),
+		uintptr(unsafe.Pointer(&freeBytes)),
+		uintptr(unsafe.Pointer(&totalBytes)),
+		uintptr(unsafe.Pointer(&availBytes)))
+
+	return FsStat{
+		Capacity:  totalBytes,
+		Available: availBytes,
+	}, nil
+}
diff --git a/go.mod b/go.mod
index 9e51c0445..8398c98a3 100644
--- a/go.mod
+++ b/go.mod
@@ -5,30 +5,30 @@ go 1.13
 require (
 	github.com/detailyang/go-fallocate v0.0.0-20180908115635-432fa640bd2e
 	github.com/elastic/go-sysinfo v1.3.0
-	github.com/filecoin-project/filecoin-ffi v0.0.0-20200326153646-e899cc1dd072
-	github.com/filecoin-project/go-bitfield v0.0.2-0.20200518150651-562fdb554b6e
-	github.com/filecoin-project/go-fil-commcid v0.0.0-20200208005934-2b8bd03caca5
-	github.com/filecoin-project/go-paramfetch v0.0.1
-	github.com/filecoin-project/specs-actors v0.6.1
+	github.com/filecoin-project/filecoin-ffi v0.30.4-0.20200716204036-cddc56607e1d
+	github.com/filecoin-project/go-bitfield v0.1.2
+	github.com/filecoin-project/go-fil-commcid v0.0.0-20200716160307-8f644712406f
+	github.com/filecoin-project/go-paramfetch v0.0.2-0.20200218225740-47c639bab663
+	github.com/filecoin-project/specs-actors v0.8.2
 	github.com/filecoin-project/specs-storage v0.1.1-0.20200622113353-88a9704877ea
 	github.com/google/uuid v1.1.1
 	github.com/gorilla/mux v1.7.4
 	github.com/hashicorp/go-multierror v1.0.0
-	github.com/ipfs/go-cid v0.0.5
+	github.com/ipfs/go-cid v0.0.6
 	github.com/ipfs/go-ipfs-files v0.0.7
-	github.com/ipfs/go-log v1.0.3
-	github.com/ipfs/go-log/v2 v2.0.3
+	github.com/ipfs/go-ipld-cbor v0.0.5-0.20200204214505-252690b78669 // indirect
+	github.com/ipfs/go-log v1.0.4
+	github.com/ipfs/go-log/v2 v2.0.5
 	github.com/mattn/go-isatty v0.0.9 // indirect
 	github.com/mitchellh/go-homedir v1.1.0
-	github.com/stretchr/testify v1.4.0
+	github.com/stretchr/testify v1.6.1
 	go.opencensus.io v0.22.3
-	go.uber.org/atomic v1.5.1 // indirect
-	go.uber.org/zap v1.13.0 // indirect
-	golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413 // indirect
-	golang.org/x/lint v0.0.0-20191125180803-fdd1cda4f05f // indirect
-	golang.org/x/sys v0.0.0-20200107162124-548cf772de50 // indirect
-	golang.org/x/tools v0.0.0-20200108195415-316d2f248479 // indirect
+	golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6 // indirect
+	golang.org/x/lint v0.0.0-20200302205851-738671d3881b // indirect
+	golang.org/x/sys v0.0.0-20200317113312-5766fd39f98d // indirect
+	golang.org/x/tools v0.0.0-20200318150045-ba25ddc85566 // indirect
 	golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543
+	honnef.co/go/tools v0.0.1-2020.1.3 // indirect
 )
 
 replace github.com/filecoin-project/filecoin-ffi => ./extern/filecoin-ffi
diff --git a/go.sum b/go.sum
index 2f97216e3..942ff725c 100644
--- a/go.sum
+++ b/go.sum
@@ -2,7 +2,6 @@ cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMT
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/aead/siphash v1.0.1/go.mod h1:Nywa3cDsYNNK3gaciGTWPwHt0wlpNV15vwmswBAUSII=
-github.com/btcsuite/btcd v0.20.1-beta h1:Ik4hyJqN8Jfyv3S4AGBOmyouMsYE3EdYODkMbQjwPGw=
 github.com/btcsuite/btcd v0.20.1-beta/go.mod h1:wVuoA8VJLEcwgqHBwHmzLRazpKxTv13Px/pDuV7OomQ=
 github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f/go.mod h1:TdznJufoqS23FtqVCzL0ZqgP5MqXbb4fg/WgDys70nA=
 github.com/btcsuite/btcutil v0.0.0-20190425235716-9e5f4b9a998d/go.mod h1:+5NJ2+qvTyV9exUAL/rxXi3DcLg2Ts+ymUAY5y4NvMg=
@@ -31,20 +30,21 @@ github.com/filecoin-project/go-address v0.0.2-0.20200218010043-eb9bb40ed5be h1:T
 github.com/filecoin-project/go-address v0.0.2-0.20200218010043-eb9bb40ed5be/go.mod h1:SAOwJoakQ8EPjwNIsiakIQKsoKdkcbx8U3IapgCg9R0=
 github.com/filecoin-project/go-amt-ipld/v2 v2.0.1-0.20200131012142-05d80eeccc5e/go.mod h1:boRtQhzmxNocrMxOXo1NYn4oUc1NGvR8tEa79wApNXg=
 github.com/filecoin-project/go-amt-ipld/v2 v2.0.1-0.20200424220931-6263827e49f2/go.mod h1:boRtQhzmxNocrMxOXo1NYn4oUc1NGvR8tEa79wApNXg=
+github.com/filecoin-project/go-amt-ipld/v2 v2.1.0/go.mod h1:nfFPoGyX0CU9SkXX8EoCcSuHN1XcbN0c6KBh7yvP5fs=
 github.com/filecoin-project/go-bitfield v0.0.0-20200416002808-b3ee67ec9060/go.mod h1:iodsLxOFZnqKtjj2zkgqzoGNrv6vUqj69AT/J8DKXEw=
-github.com/filecoin-project/go-bitfield v0.0.1 h1:Xg/JnrqqE77aJVKdbEyR04n9FZQWhwrN+buDgQCVpZU=
 github.com/filecoin-project/go-bitfield v0.0.1/go.mod h1:Ry9/iUlWSyjPUzlAvdnfy4Gtvrq4kWmWDztCU1yEgJY=
-github.com/filecoin-project/go-bitfield v0.0.2-0.20200518150651-562fdb554b6e h1:gkG/7G+iKy4He+IiQNeQn+nndFznb/vCoOR8iRQsm60=
-github.com/filecoin-project/go-bitfield v0.0.2-0.20200518150651-562fdb554b6e/go.mod h1:Ry9/iUlWSyjPUzlAvdnfy4Gtvrq4kWmWDztCU1yEgJY=
+github.com/filecoin-project/go-bitfield v0.1.2 h1:TjLregCoyP1/5lm7WCM0axyV1myIHwbjGa21skuu5tk=
+github.com/filecoin-project/go-bitfield v0.1.2/go.mod h1:CNl9WG8hgR5mttCnUErjcQjGvuiZjRqK9rHVBsQF4oM=
 github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03 h1:2pMXdBnCiXjfCYx/hLqFxccPoqsSveQFxVLvNxy9bus=
 github.com/filecoin-project/go-crypto v0.0.0-20191218222705-effae4ea9f03/go.mod h1:+viYnvGtUTgJRdy6oaeF4MTFKAfatX071MPDPBL11EQ=
-github.com/filecoin-project/go-fil-commcid v0.0.0-20200208005934-2b8bd03caca5 h1:yvQJCW9mmi9zy+51xA01Ea2X7/dL7r8eKDPuGUjRmbo=
-github.com/filecoin-project/go-fil-commcid v0.0.0-20200208005934-2b8bd03caca5/go.mod h1:JbkIgFF/Z9BDlvrJO1FuKkaWsH673/UdFaiVS6uIHlA=
-github.com/filecoin-project/go-paramfetch v0.0.1 h1:gV7bs5YaqlgpGFMiLxInGK2L1FyCXUE0rimz4L7ghoE=
-github.com/filecoin-project/go-paramfetch v0.0.1/go.mod h1:fZzmf4tftbwf9S37XRifoJlz7nCjRdIrMGLR07dKLCc=
+github.com/filecoin-project/go-fil-commcid v0.0.0-20200716160307-8f644712406f h1:GxJzR3oRIMTPtpZ0b7QF8FKPK6/iPAc7trhlL5k/g+s=
+github.com/filecoin-project/go-fil-commcid v0.0.0-20200716160307-8f644712406f/go.mod h1:Eaox7Hvus1JgPrL5+M3+h7aSPHc0cVqpSxA+TxIEpZQ=
+github.com/filecoin-project/go-paramfetch v0.0.2-0.20200218225740-47c639bab663 h1:eYxi6vI5CyeXD15X1bB3bledDXbqKxqf0wQzTLgwYwA=
+github.com/filecoin-project/go-paramfetch v0.0.2-0.20200218225740-47c639bab663/go.mod h1:fZzmf4tftbwf9S37XRifoJlz7nCjRdIrMGLR07dKLCc=
 github.com/filecoin-project/specs-actors v0.3.0/go.mod h1:nQYnFbQ7Y0bHZyq6HDEuVlCPR+U3z5Q3wMOQ+2aiV+Y=
-github.com/filecoin-project/specs-actors v0.6.1 h1:rhHlEzqcuuQU6oKc4csuq+/kQBDZ4EXtSomoN2XApCA=
 github.com/filecoin-project/specs-actors v0.6.1/go.mod h1:dRdy3cURykh2R8O/DKqy8olScl70rmIS7GrB4hB1IDY=
+github.com/filecoin-project/specs-actors v0.8.2 h1:fpAPOPqWqmzJCWHpm6P1XDRSpQrxyY5Pzh5H3doYs7Q=
+github.com/filecoin-project/specs-actors v0.8.2/go.mod h1:Q3ACV5kBLvqPaYbthc/J1lGMJ5OwogmD9pzdtPRMdCw=
 github.com/filecoin-project/specs-storage v0.1.1-0.20200622113353-88a9704877ea h1:iixjULRQFPn7Q9KlIqfwLJnlAXO10bbkI+xy5GKGdLY=
 github.com/filecoin-project/specs-storage v0.1.1-0.20200622113353-88a9704877ea/go.mod h1:Pr5ntAaxsh+sLG/LYiL4tKzvA83Vk5vLODYhfNwOg7k=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
@@ -58,6 +58,7 @@ github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfb
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
 github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
@@ -82,7 +83,11 @@ github.com/ipfs/go-cid v0.0.2/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUP
 github.com/ipfs/go-cid v0.0.3/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
 github.com/ipfs/go-cid v0.0.5 h1:o0Ix8e/ql7Zb5UVUJEUfjsWCIY8t48++9lR8qi6oiJU=
 github.com/ipfs/go-cid v0.0.5/go.mod h1:plgt+Y5MnOey4vO4UlUazGqdbEXuFYitED67FexhXog=
+github.com/ipfs/go-cid v0.0.6-0.20200501230655-7c82f3b81c00/go.mod h1:plgt+Y5MnOey4vO4UlUazGqdbEXuFYitED67FexhXog=
+github.com/ipfs/go-cid v0.0.6 h1:go0y+GcDOGeJIV01FeBsta4FHngoA4Wz7KMeLkXAhMs=
+github.com/ipfs/go-cid v0.0.6/go.mod h1:6Ux9z5e+HpkQdckYoX1PG/6xqKspzlEIR5SDmgqgC/I=
 github.com/ipfs/go-hamt-ipld v0.0.15-0.20200131012125-dd88a59d3f2e/go.mod h1:9aQJu/i/TaRDW6jqB5U217dLIDopn50wxLdHXM2CTfE=
+github.com/ipfs/go-hamt-ipld v0.1.1/go.mod h1:1EZCr2v0jlCnhpa+aZ0JZYp8Tt2w16+JJOAVz17YcDk=
 github.com/ipfs/go-ipfs-files v0.0.7 h1:s5BRD12ndahqYifeH1S8Z73zqZhR+3IdKYAG9PiETs0=
 github.com/ipfs/go-ipfs-files v0.0.7/go.mod h1:wiN/jSG8FKyk7N0WyctKSvq3ljIa2NNTiZB55kpTdOs=
 github.com/ipfs/go-ipfs-util v0.0.1 h1:Wz9bL2wB2YBJqggkA4dD7oSmqB4cAnpNbGrlHJulv50=
@@ -90,16 +95,18 @@ github.com/ipfs/go-ipfs-util v0.0.1/go.mod h1:spsl5z8KUnrve+73pOhSVZND1SIxPW5RyB
 github.com/ipfs/go-ipld-cbor v0.0.3/go.mod h1:wTBtrQZA3SoFKMVkp6cn6HMRteIB1VsmHA0AQFOn7Nc=
 github.com/ipfs/go-ipld-cbor v0.0.4 h1:Aw3KPOKXjvrm6VjwJvFf1F1ekR/BH3jdof3Bk7OTiSA=
 github.com/ipfs/go-ipld-cbor v0.0.4/go.mod h1:BkCduEx3XBCO6t2Sfo5BaHzuok7hbhdMm9Oh8B2Ftq4=
+github.com/ipfs/go-ipld-cbor v0.0.5-0.20200204214505-252690b78669 h1:jIVle1vGSzxyUhseYNEqd7qcDVRrIbJ7UxGwao70cF0=
+github.com/ipfs/go-ipld-cbor v0.0.5-0.20200204214505-252690b78669/go.mod h1:BkCduEx3XBCO6t2Sfo5BaHzuok7hbhdMm9Oh8B2Ftq4=
 github.com/ipfs/go-ipld-format v0.0.1 h1:HCu4eB/Gh+KD/Q0M8u888RFkorTWNIL3da4oc5dwc80=
 github.com/ipfs/go-ipld-format v0.0.1/go.mod h1:kyJtbkDALmFHv3QR6et67i35QzO3S0dCDnkOJhcZkms=
 github.com/ipfs/go-ipld-format v0.0.2 h1:OVAGlyYT6JPZ0pEfGntFPS40lfrDmaDbQwNHEY2G9Zs=
 github.com/ipfs/go-ipld-format v0.0.2/go.mod h1:4B6+FM2u9OJ9zCV+kSbgFAZlOrv1Hqbf0INGQgiKf9k=
 github.com/ipfs/go-log v0.0.1/go.mod h1:kL1d2/hzSpI0thNYjiKfjanbVNU+IIGA/WnNESY9leM=
 github.com/ipfs/go-log v1.0.0/go.mod h1:JO7RzlMK6rA+CIxFMLOuB6Wf5b81GDiKElL7UPSIKjA=
-github.com/ipfs/go-log v1.0.3 h1:Gg7SUYSZ7BrqaKMwM+hRgcAkKv4QLfzP4XPQt5Sx/OI=
-github.com/ipfs/go-log v1.0.3/go.mod h1:OsLySYkwIbiSUR/yBTdv1qPtcE4FW3WPWk/ewz9Ru+A=
-github.com/ipfs/go-log/v2 v2.0.3 h1:Q2gXcBoCALyLN/pUQlz1qgu0x3uFV6FzP9oXhpfyJpc=
-github.com/ipfs/go-log/v2 v2.0.3/go.mod h1:O7P1lJt27vWHhOwQmcFEvlmo49ry2VY2+JfBWFaa9+0=
+github.com/ipfs/go-log v1.0.4 h1:6nLQdX4W8P9yZZFH7mO+X/PzjN8Laozm/lMJ6esdgzY=
+github.com/ipfs/go-log v1.0.4/go.mod h1:oDCg2FkjogeFOhqqb+N39l2RpTNPL6F/StPkB3kPgcs=
+github.com/ipfs/go-log/v2 v2.0.5 h1:fL4YI+1g5V/b1Yxr1qAiXTMg1H8z9vx/VmJxBuQMHvU=
+github.com/ipfs/go-log/v2 v2.0.5/go.mod h1:eZs4Xt4ZUJQFM3DlanGhy7TkwwawCZcSByscwkWG+dw=
 github.com/ipsn/go-secp256k1 v0.0.0-20180726113642-9d62b9f0bc52 h1:QG4CGBqCeuBo6aZlGAamSkxWdgWfZGeE49eUOWJPA4c=
 github.com/ipsn/go-secp256k1 v0.0.0-20180726113642-9d62b9f0bc52/go.mod h1:fdg+/X9Gg4AsAIzWpEHwnqd+QY3b7lajxyjE1m4hkq4=
 github.com/jbenet/go-cienv v0.1.0/go.mod h1:TqNnHUmJgXau0nCzC7kXWeotg3J9W34CUv5Djy1+FlA=
@@ -125,9 +132,7 @@ github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/libp2p/go-flow-metrics v0.0.3/go.mod h1:HeoSNUrOJVK1jEpDqVEiUOIXqhbnS27omG0uWU5slZs=
-github.com/libp2p/go-libp2p-core v0.3.0 h1:F7PqduvrztDtFsAa/bcheQ3azmNo+Nq7m8hQY5GiUW8=
 github.com/libp2p/go-libp2p-core v0.3.0/go.mod h1:ACp3DmS3/N64c2jDzcV429ukDpicbL6+TrrxANBjPGw=
-github.com/libp2p/go-openssl v0.0.4 h1:d27YZvLoTyMhIN4njrkr8zMDOM4lfpHIp6A+TK9fovg=
 github.com/libp2p/go-openssl v0.0.4/go.mod h1:unDrJpgy3oFr+rqXsarWifmJuNnJR4chtO1HmaZjggc=
 github.com/mailru/easyjson v0.0.0-20180823135443-60711f1a8329/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
@@ -157,15 +162,20 @@ github.com/mr-tron/base58 v1.1.3 h1:v+sk57XuaCKGXpWtVBX8YJzO7hMGx4Aajh4TQbdEFdc=
 github.com/mr-tron/base58 v1.1.3/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
 github.com/multiformats/go-base32 v0.0.3 h1:tw5+NhuwaOjJCC5Pp82QuXbrmLzWg7uxlMFp8Nq/kkI=
 github.com/multiformats/go-base32 v0.0.3/go.mod h1:pLiuGC8y0QR3Ue4Zug5UzK9LjgbkL8NSQj0zQ5Nz/AA=
-github.com/multiformats/go-multiaddr v0.2.0 h1:lR52sFwcTCuQb6bTfnXF6zA2XfyYvyd+5a9qECv/J90=
+github.com/multiformats/go-base36 v0.1.0 h1:JR6TyF7JjGd3m6FbLU2cOxhC0Li8z8dLNGQ89tUg4F4=
+github.com/multiformats/go-base36 v0.1.0/go.mod h1:kFGE83c6s80PklsHO9sRn2NCoffoRdUUOENyW/Vv6sM=
 github.com/multiformats/go-multiaddr v0.2.0/go.mod h1:0nO36NvPpyV4QzvTLi/lafl2y95ncPj0vFwVF6k6wJ4=
 github.com/multiformats/go-multibase v0.0.1 h1:PN9/v21eLywrFWdFNsFKaU04kLJzuYzmrJR+ubhT9qA=
 github.com/multiformats/go-multibase v0.0.1/go.mod h1:bja2MqRZ3ggyXtZSEDKpl0uO/gviWFaSteVbWT51qgs=
+github.com/multiformats/go-multibase v0.0.3 h1:l/B6bJDQjvQ5G52jw4QGSYeOTZoAwIO77RblWplfIqk=
+github.com/multiformats/go-multibase v0.0.3/go.mod h1:5+1R4eQrT3PkYZ24C3W2Ue2tPwIdYQD509ZjSb5y9Oc=
 github.com/multiformats/go-multihash v0.0.1/go.mod h1:w/5tugSrLEbWqlcgJabL3oHFKTwfvkofsjW2Qa1ct4U=
 github.com/multiformats/go-multihash v0.0.8/go.mod h1:YSLudS+Pi8NHE7o6tb3D8vrpKa63epEDmG8nTduyAew=
 github.com/multiformats/go-multihash v0.0.10/go.mod h1:YSLudS+Pi8NHE7o6tb3D8vrpKa63epEDmG8nTduyAew=
 github.com/multiformats/go-multihash v0.0.13 h1:06x+mk/zj1FoMsgNejLpy6QTvJqlSt/BhLEy87zidlc=
 github.com/multiformats/go-multihash v0.0.13/go.mod h1:VdAWLKTwram9oKAatUcLxBNUjdtcVwxObEQBtRfuyjc=
+github.com/multiformats/go-multihash v0.0.14 h1:QoBceQYQQtNUuf6s7wHxnE2c8bhbMqhfGzNI032se/I=
+github.com/multiformats/go-multihash v0.0.14/go.mod h1:VdAWLKTwram9oKAatUcLxBNUjdtcVwxObEQBtRfuyjc=
 github.com/multiformats/go-varint v0.0.1/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
 github.com/multiformats/go-varint v0.0.2/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
 github.com/multiformats/go-varint v0.0.5 h1:XVZwSo04Cs3j/jS0uAEPpT3JY6DzMcVLLoWOSnCxOjg=
@@ -199,7 +209,6 @@ github.com/smartystreets/goconvey v0.0.0-20190222223459-a17d461953aa/go.mod h1:2
 github.com/smartystreets/goconvey v0.0.0-20190731233626-505e41936337 h1:WN9BUFbdyOsSH/XohnWpXOlq9NBD5sGAB2FciQMUEe8=
 github.com/smartystreets/goconvey v0.0.0-20190731233626-505e41936337/go.mod h1:syvi0/a8iFYH4r/RixwvyeAJjdLS9QV7WQ/tjFTllLA=
 github.com/smola/gocompat v0.2.0/go.mod h1:1B0MlxbmoZNo3h8guHp8HztB3BSYR5itql9qtVc0ypY=
-github.com/spacemonkeygo/spacelog v0.0.0-20180420211403-2296661a0572 h1:RC6RW7j+1+HkWaX/Yh71Ee5ZHaHYt7ZP4sQgUrm6cDU=
 github.com/spacemonkeygo/spacelog v0.0.0-20180420211403-2296661a0572/go.mod h1:w0SWMsp6j9O/dk4/ZpIhL+3CkG8ofA2vuv7k+ltqUMc=
 github.com/spaolacci/murmur3 v1.1.0 h1:7c1g84S4BPRrfL5Xrdp6fOJ206sU9y293DDHaoy0bLI=
 github.com/spaolacci/murmur3 v1.1.0/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
@@ -210,6 +219,8 @@ github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXf
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/warpfork/go-wish v0.0.0-20180510122957-5ad1f5abf436 h1:qOpVTI+BrstcjTZLm2Yz/3sOnqkzj3FQoh0g+E5s3Gc=
 github.com/warpfork/go-wish v0.0.0-20180510122957-5ad1f5abf436/go.mod h1:x6AKhvSSexNrVSrViXSHUEbICjmGXhtgABaHIySUSGw=
 github.com/warpfork/go-wish v0.0.0-20190328234359-8b3e70f8e830 h1:8kxMKmKzXXL4Ru1nyhvdms/JjWt+3YLpvRb/bAjO/y0=
@@ -218,27 +229,33 @@ github.com/whyrusleeping/cbor-gen v0.0.0-20191216205031-b047b6acb3c0/go.mod h1:x
 github.com/whyrusleeping/cbor-gen v0.0.0-20200123233031-1cdf64d27158/go.mod h1:Xj/M2wWU+QdTdRbu/L/1dIZY8/Wb2K9pAhtroQuxJJI=
 github.com/whyrusleeping/cbor-gen v0.0.0-20200414195334-429a0b5e922e h1:JY8o/ebUUrCYetWmjRCNghxC59cOEaili83rxPRQCLw=
 github.com/whyrusleeping/cbor-gen v0.0.0-20200414195334-429a0b5e922e/go.mod h1:Xj/M2wWU+QdTdRbu/L/1dIZY8/Wb2K9pAhtroQuxJJI=
+github.com/whyrusleeping/cbor-gen v0.0.0-20200504204219-64967432584d/go.mod h1:W5MvapuoHRP8rz4vxjwCK1pDqF1aQcWsV5PZ+AHbqdg=
+github.com/whyrusleeping/cbor-gen v0.0.0-20200715143311-227fab5a2377 h1:LHFlP/ktDvOnCap7PsT87cs7Gwd0p+qv6Qm5g2ZPR+I=
+github.com/whyrusleeping/cbor-gen v0.0.0-20200715143311-227fab5a2377/go.mod h1:fgkXqYy7bV2cFeIEOkVTZS/WjXARfBqSH6Q2qHL33hQ=
 github.com/whyrusleeping/go-logging v0.0.0-20170515211332-0457bb6b88fc/go.mod h1:bopw91TMyo8J3tvftk8xmU2kPmlrt4nScJQZU2hE5EM=
 github.com/x-cray/logrus-prefixed-formatter v0.5.2/go.mod h1:2duySbKsL6M18s5GU7VPsoEPHyzalCE06qoARUCeBBE=
+github.com/xorcare/golden v0.6.0/go.mod h1:7T39/ZMvaSEZlBPoYfVFmsBLmUl3uz9IuzWj/U6FtvQ=
+github.com/yuin/goldmark v1.1.25/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 go.opencensus.io v0.22.2/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.3 h1:8sGtKOrtQqkN1bp2AtX+misvLIlOmsEsNd+9NIcPEm8=
 go.opencensus.io v0.22.3/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.uber.org/atomic v1.4.0 h1:cxzIVoETapQEqDhQu3QfnvXAV4AlzcvUCxkVUFw3+EU=
 go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/atomic v1.5.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
-go.uber.org/atomic v1.5.1 h1:rsqfU5vBkVknbhUGbAUwQKR2H4ItV8tjJ+6kJX4cxHM=
-go.uber.org/atomic v1.5.1/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
+go.uber.org/atomic v1.6.0 h1:Ezj3JGmsOnG1MoRWQkPBsKLe9DwWD9QeXzTRzzldNVk=
+go.uber.org/atomic v1.6.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
 go.uber.org/multierr v1.1.0 h1:HoEmRHQPVSqub6w2z2d2EOVs2fjyFRGyofhKuyDq0QI=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
-go.uber.org/multierr v1.3.0/go.mod h1:VgVr7evmIr6uPjLBxg28wmKNXyqE9akIJ5XnfpiKl+4=
 go.uber.org/multierr v1.4.0 h1:f3WCSC2KzAcBXGATIxAB1E2XuCpNU255wNKZ505qi3E=
 go.uber.org/multierr v1.4.0/go.mod h1:VgVr7evmIr6uPjLBxg28wmKNXyqE9akIJ5XnfpiKl+4=
+go.uber.org/multierr v1.5.0 h1:KCa4XfM8CWFCpxXRGok+Q0SS/0XBhMDbHHGABQLvD2A=
+go.uber.org/multierr v1.5.0/go.mod h1:FeouvMocqHpRaaGuG9EjoKcStLC43Zu/fmqdUMPcKYU=
 go.uber.org/tools v0.0.0-20190618225709-2cfd321de3ee h1:0mgffUl7nfd+FpvXMVz4IDEaUSmT1ysygQC7qYo7sG4=
 go.uber.org/tools v0.0.0-20190618225709-2cfd321de3ee/go.mod h1:vJERXedbb3MVM5f9Ejo0C68/HhF8uaILCdgjnY+goOA=
 go.uber.org/zap v1.10.0 h1:ORx85nbTijNz8ljznvCMR1ZBIPKFn3jQrag10X2AsuM=
 go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
-go.uber.org/zap v1.13.0 h1:nR6NoDBgAf67s68NhaXbsojM+2gxp3S1hWkHDl27pVU=
-go.uber.org/zap v1.13.0/go.mod h1:zwrFLgMcdUuIBviXEYEH1YKNaOBnKXsx2IPda5bBwHM=
+go.uber.org/zap v1.14.1 h1:nYDKopTbvAPq/NrUVZwT15y2lpROBiLLyoRTbXOYWOo=
+go.uber.org/zap v1.14.1/go.mod h1:Mb2vm2krFEG5DV0W9qcHBYFtp/Wku1cvYaqPsS/WYfc=
 golang.org/x/crypto v0.0.0-20170930174604-9419663f5a44/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190211182817-74369b46fc67/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
@@ -247,17 +264,19 @@ golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8U
 golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550 h1:ObdrDkeb4kJdCP557AjRjq69pTHfNouLtWZG7j9rPN8=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413 h1:ULYEB3JvPRE/IfO+9uO7vKV/xzVTO7XPAwm8xbf4w2g=
-golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6 h1:TjszyFsQsyZNHwdVdZ5m7bjmreu0znc2kRYsEml9/Ww=
+golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
 golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
-golang.org/x/lint v0.0.0-20191125180803-fdd1cda4f05f h1:J5lckAjkw6qYlOZNj90mLYNTEKDvWeuc1yieZ8qUzUE=
-golang.org/x/lint v0.0.0-20191125180803-fdd1cda4f05f/go.mod h1:5qLYkcX4OjUUV8bRuDixDT3tpyyb+LUpUlRWLxfhWrs=
+golang.org/x/lint v0.0.0-20200302205851-738671d3881b h1:Wh+f8QHJXR411sJR8/vRBTZ7YapZaRvUcLFFJhusH0k=
+golang.org/x/lint v0.0.0-20200302205851-738671d3881b/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
 golang.org/x/mod v0.0.0-20190513183733-4bf6d317e70e/go.mod h1:mXi4GBBbnImb6dmsKGUJ2LatrhH/nqhxcFungHvyanc=
 golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
+golang.org/x/mod v0.2.0 h1:KU7oHjnv3XNWfa5COkzUifxZmxp1TyI7ImMXqFxLwvQ=
+golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
@@ -266,12 +285,14 @@ golang.org/x/net v0.0.0-20190227160552-c95aed5357e7/go.mod h1:mL1N/T3taQHkDXs73r
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200226121028-0de0cce0169b/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180202135801-37707fdb30a5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -287,8 +308,8 @@ golang.org/x/sys v0.0.0-20190813064441-fde4db37ae7a/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20190826190057-c7b8b68b1456/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191025021431-6c3a3bfe00ae h1:QoJmnb9uyPCrH8GIg9uRLn4Ta45yhcQtpymCd0AavO8=
 golang.org/x/sys v0.0.0-20191025021431-6c3a3bfe00ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200107162124-548cf772de50 h1:YvQ10rzcqWXLlJZ3XCUoO25savxmscf4+SC+ZqiCHhA=
-golang.org/x/sys v0.0.0-20200107162124-548cf772de50/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200317113312-5766fd39f98d h1:62ap6LNOjDU6uGmKXHJbSfciMoV+FeI1sRXx/pLDL44=
+golang.org/x/sys v0.0.0-20200317113312-5766fd39f98d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/tools v0.0.0-20180221164845-07fd8470d635/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
@@ -302,9 +323,11 @@ golang.org/x/tools v0.0.0-20190328211700-ab21143f2384/go.mod h1:LCzVGOaR6xXOjkQ3
 golang.org/x/tools v0.0.0-20190621195816-6e04913cbbac/go.mod h1:/rFqwRUd4F7ZHNgwSSTFct+R/Kf4OFW1sUzUTQQTgfc=
 golang.org/x/tools v0.0.0-20191029041327-9cc4af7d6b2c/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.0.0-20191029190741-b9c20aec41a5/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.0.0-20191125144606-a911d9008d1f/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.0.0-20200108195415-316d2f248479 h1:csuS+MHeEA2eWhyjQCMaPMq4z1+/PohkBSjJZHSIbOE=
-golang.org/x/tools v0.0.0-20200108195415-316d2f248479/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20191130070609-6e064ea0cf2d/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20200130002326-2f3ba24bd6e7/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
+golang.org/x/tools v0.0.0-20200318150045-ba25ddc85566 h1:OXjomkWHhzUx4+HldlJ2TsMxJdWgEo5CTtspD1wdhdk=
+golang.org/x/tools v0.0.0-20200318150045-ba25ddc85566/go.mod h1:Sl4aGygMT6LrqrWclx+PTx3U+LnKx/seiNR+3G19Ar8=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
@@ -330,8 +353,12 @@ gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4 h1:/eiJrUcujPVeJ3xlSWaiNi3uSVmDGBK1pDHUHAnao1I=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.1-2019.2.3 h1:3JgtbtFHMiCmsznwGVTUWbgGov+pVqnlf1dEJTNAXeM=
 honnef.co/go/tools v0.0.1-2019.2.3/go.mod h1:a3bituU0lyd329TUQxRnasdCoJDkEUEAqEt0JzvZhAg=
+honnef.co/go/tools v0.0.1-2020.1.3 h1:sXmLre5bzIR6ypkjXCDI3jHPssRhc8KD/Ome589sc3U=
+honnef.co/go/tools v0.0.1-2020.1.3/go.mod h1:X/FiERA/W4tHapMX5mGpAtMSVEeEUOyHaw9vFzvIQ3k=
 howett.net/plist v0.0.0-20181124034731-591f970eefbb h1:jhnBjNi9UFpfpl8YZhA9CrOqpnJdvzuiHsl/dnxl11M=
 howett.net/plist v0.0.0-20181124034731-591f970eefbb/go.mod h1:vMygbs4qMhSZSc4lCUl2OEE+rDiIIJAIdR4m7MiMcm0=
diff --git a/localworker.go b/localworker.go
index a1d82209a..14ed1cd0b 100644
--- a/localworker.go
+++ b/localworker.go
@@ -61,14 +61,22 @@ type localWorkerPathProvider struct {
 }
 
 func (l *localWorkerPathProvider) AcquireSector(ctx context.Context, sector abi.SectorID, existing stores.SectorFileType, allocate stores.SectorFileType, sealing stores.PathType) (stores.SectorPaths, func(), error) {
+
 	paths, storageIDs, err := l.w.storage.AcquireSector(ctx, sector, l.w.scfg.SealProofType, existing, allocate, sealing, l.op)
 	if err != nil {
 		return stores.SectorPaths{}, nil, err
 	}
 
+	releaseStorage, err := l.w.localStore.Reserve(ctx, sector, l.w.scfg.SealProofType, allocate, storageIDs, stores.FSOverheadSeal)
+	if err != nil {
+		return stores.SectorPaths{}, nil, xerrors.Errorf("reserving storage space: %w", err)
+	}
+
 	log.Debugf("acquired sector %d (e:%d; a:%d): %v", sector, existing, allocate, paths)
 
 	return paths, func() {
+		releaseStorage()
+
 		for _, fileType := range pathTypes {
 			if fileType&allocate == 0 {
 				continue
@@ -171,8 +179,10 @@ func (l *LocalWorker) FinalizeSector(ctx context.Context, sector abi.SectorID, k
 		return xerrors.Errorf("finalizing sector: %w", err)
 	}
 
-	if err := l.storage.Remove(ctx, sector, stores.FTUnsealed, true); err != nil {
-		return xerrors.Errorf("removing unsealed data: %w", err)
+	if len(keepUnsealed) == 0 {
+		if err := l.storage.Remove(ctx, sector, stores.FTUnsealed, true); err != nil {
+			return xerrors.Errorf("removing unsealed data: %w", err)
+		}
 	}
 
 	return nil
@@ -227,10 +237,10 @@ func (l *LocalWorker) UnsealPiece(ctx context.Context, sector abi.SectorID, inde
 	return nil
 }
 
-func (l *LocalWorker) ReadPiece(ctx context.Context, writer io.Writer, sector abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) error {
+func (l *LocalWorker) ReadPiece(ctx context.Context, writer io.Writer, sector abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) (bool, error) {
 	sb, err := l.sb()
 	if err != nil {
-		return err
+		return false, err
 	}
 
 	return sb.ReadPiece(ctx, writer, sector, index, size)
diff --git a/manager.go b/manager.go
index caea09cd0..303df2169 100644
--- a/manager.go
+++ b/manager.go
@@ -3,6 +3,7 @@ package sectorstorage
 import (
 	"context"
 	"errors"
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"io"
 	"net/http"
 
@@ -33,7 +34,7 @@ type Worker interface {
 
 	Fetch(ctx context.Context, s abi.SectorID, ft stores.SectorFileType, ptype stores.PathType, am stores.AcquireMode) error
 	UnsealPiece(context.Context, abi.SectorID, storiface.UnpaddedByteIndex, abi.UnpaddedPieceSize, abi.SealRandomness, cid.Cid) error
-	ReadPiece(context.Context, io.Writer, abi.SectorID, storiface.UnpaddedByteIndex, abi.UnpaddedPieceSize) error
+	ReadPiece(context.Context, io.Writer, abi.SectorID, storiface.UnpaddedByteIndex, abi.UnpaddedPieceSize) (bool, error)
 
 	TaskTypes(context.Context) (map[sealtasks.TaskType]struct{}, error)
 
@@ -75,6 +76,8 @@ type Manager struct {
 }
 
 type SealerConfig struct {
+	ParallelFetchLimit int
+
 	// Local worker config
 	AllowPreCommit1 bool
 	AllowPreCommit2 bool
@@ -95,7 +98,7 @@ func New(ctx context.Context, ls stores.LocalStorage, si stores.SectorIndex, cfg
 		return nil, xerrors.Errorf("creating prover instance: %w", err)
 	}
 
-	stor := stores.NewRemote(lstor, si, http.Header(sa))
+	stor := stores.NewRemote(lstor, si, http.Header(sa), sc.ParallelFetchLimit)
 
 	m := &Manager{
 		scfg: cfg,
@@ -165,7 +168,10 @@ func (m *Manager) AddWorker(ctx context.Context, w Worker) error {
 	}
 
 	m.sched.newWorkers <- &workerHandle{
-		w:         w,
+		w: w,
+		wt: &workTracker{
+			running: map[uint64]storiface.WorkerJob{},
+		},
 		info:      info,
 		preparing: &activeResources{},
 		active:    &activeResources{},
@@ -207,23 +213,38 @@ func (m *Manager) ReadPiece(ctx context.Context, sink io.Writer, sector abi.Sect
 
 	var selector WorkerSelector
 	if len(best) == 0 { // new
-		selector, err = newAllocSelector(ctx, m.index, stores.FTUnsealed, stores.PathSealing)
+		selector = newAllocSelector(m.index, stores.FTUnsealed, stores.PathSealing)
 	} else { // append to existing
-		selector, err = newExistingSelector(ctx, m.index, sector, stores.FTUnsealed, false)
-	}
-	if err != nil {
-		return xerrors.Errorf("creating unsealPiece selector: %w", err)
+		selector = newExistingSelector(m.index, sector, stores.FTUnsealed, false)
 	}
 
-	// TODO: Optimization: don't send unseal to a worker if the requested range is already unsealed
+	var readOk bool
+
+	if len(best) > 0 {
+		// There is unsealed sector, see if we can read from it
+
+		selector = newExistingSelector(m.index, sector, stores.FTUnsealed, false)
+
+		err = m.sched.Schedule(ctx, sector, sealtasks.TTReadUnsealed, selector, schedFetch(sector, stores.FTUnsealed, stores.PathSealing, stores.AcquireMove), func(ctx context.Context, w Worker) error {
+			readOk, err = w.ReadPiece(ctx, sink, sector, offset, size)
+			return err
+		})
+		if err != nil {
+			return xerrors.Errorf("reading piece from sealed sector: %w", err)
+		}
+
+		if readOk {
+			return nil
+		}
+	}
 
 	unsealFetch := func(ctx context.Context, worker Worker) error {
-		if err := worker.Fetch(ctx, sector, stores.FTSealed|stores.FTCache, true, stores.AcquireCopy); err != nil {
+		if err := worker.Fetch(ctx, sector, stores.FTSealed|stores.FTCache, stores.PathSealing, stores.AcquireCopy); err != nil {
 			return xerrors.Errorf("copy sealed/cache sector data: %w", err)
 		}
 
 		if len(best) > 0 {
-			if err := worker.Fetch(ctx, sector, stores.FTUnsealed, true, stores.AcquireMove); err != nil {
+			if err := worker.Fetch(ctx, sector, stores.FTUnsealed, stores.PathSealing, stores.AcquireMove); err != nil {
 				return xerrors.Errorf("copy unsealed sector data: %w", err)
 			}
 		}
@@ -237,18 +258,20 @@ func (m *Manager) ReadPiece(ctx context.Context, sink io.Writer, sector abi.Sect
 		return err
 	}
 
-	selector, err = newExistingSelector(ctx, m.index, sector, stores.FTUnsealed, false)
-	if err != nil {
-		return xerrors.Errorf("creating readPiece selector: %w", err)
-	}
+	selector = newExistingSelector(m.index, sector, stores.FTUnsealed, false)
 
 	err = m.sched.Schedule(ctx, sector, sealtasks.TTReadUnsealed, selector, schedFetch(sector, stores.FTUnsealed, stores.PathSealing, stores.AcquireMove), func(ctx context.Context, w Worker) error {
-		return w.ReadPiece(ctx, sink, sector, offset, size)
+		readOk, err = w.ReadPiece(ctx, sink, sector, offset, size)
+		return err
 	})
 	if err != nil {
 		return xerrors.Errorf("reading piece from sealed sector: %w", err)
 	}
 
+	if readOk {
+		return xerrors.Errorf("failed to read unsealed piece")
+	}
+
 	return nil
 }
 
@@ -268,12 +291,9 @@ func (m *Manager) AddPiece(ctx context.Context, sector abi.SectorID, existingPie
 	var selector WorkerSelector
 	var err error
 	if len(existingPieces) == 0 { // new
-		selector, err = newAllocSelector(ctx, m.index, stores.FTUnsealed, stores.PathSealing)
+		selector = newAllocSelector(m.index, stores.FTUnsealed, stores.PathSealing)
 	} else { // use existing
-		selector, err = newExistingSelector(ctx, m.index, sector, stores.FTUnsealed, false)
-	}
-	if err != nil {
-		return abi.PieceInfo{}, xerrors.Errorf("creating path selector: %w", err)
+		selector = newExistingSelector(m.index, sector, stores.FTUnsealed, false)
 	}
 
 	var out abi.PieceInfo
@@ -299,10 +319,7 @@ func (m *Manager) SealPreCommit1(ctx context.Context, sector abi.SectorID, ticke
 
 	// TODO: also consider where the unsealed data sits
 
-	selector, err := newAllocSelector(ctx, m.index, stores.FTCache|stores.FTSealed, stores.PathSealing)
-	if err != nil {
-		return nil, xerrors.Errorf("creating path selector: %w", err)
-	}
+	selector := newAllocSelector(m.index, stores.FTCache|stores.FTSealed, stores.PathSealing)
 
 	err = m.sched.Schedule(ctx, sector, sealtasks.TTPreCommit1, selector, schedFetch(sector, stores.FTUnsealed, stores.PathSealing, stores.AcquireMove), func(ctx context.Context, w Worker) error {
 		p, err := w.SealPreCommit1(ctx, sector, ticket, pieces)
@@ -324,10 +341,7 @@ func (m *Manager) SealPreCommit2(ctx context.Context, sector abi.SectorID, phase
 		return storage.SectorCids{}, xerrors.Errorf("acquiring sector lock: %w", err)
 	}
 
-	selector, err := newExistingSelector(ctx, m.index, sector, stores.FTCache|stores.FTSealed, true)
-	if err != nil {
-		return storage.SectorCids{}, xerrors.Errorf("creating path selector: %w", err)
-	}
+	selector := newExistingSelector(m.index, sector, stores.FTCache|stores.FTSealed, true)
 
 	err = m.sched.Schedule(ctx, sector, sealtasks.TTPreCommit2, selector, schedFetch(sector, stores.FTCache|stores.FTSealed, stores.PathSealing, stores.AcquireMove), func(ctx context.Context, w Worker) error {
 		p, err := w.SealPreCommit2(ctx, sector, phase1Out)
@@ -351,10 +365,7 @@ func (m *Manager) SealCommit1(ctx context.Context, sector abi.SectorID, ticket a
 	// NOTE: We set allowFetch to false in so that we always execute on a worker
 	// with direct access to the data. We want to do that because this step is
 	// generally very cheap / fast, and transferring data is not worth the effort
-	selector, err := newExistingSelector(ctx, m.index, sector, stores.FTCache|stores.FTSealed, false)
-	if err != nil {
-		return storage.Commit1Out{}, xerrors.Errorf("creating path selector: %w", err)
-	}
+	selector := newExistingSelector(m.index, sector, stores.FTCache|stores.FTSealed, false)
 
 	err = m.sched.Schedule(ctx, sector, sealtasks.TTCommit1, selector, schedFetch(sector, stores.FTCache|stores.FTSealed, stores.PathSealing, stores.AcquireMove), func(ctx context.Context, w Worker) error {
 		p, err := w.SealCommit1(ctx, sector, ticket, seed, pieces, cids)
@@ -402,12 +413,9 @@ func (m *Manager) FinalizeSector(ctx context.Context, sector abi.SectorID, keepU
 		}
 	}
 
-	selector, err := newExistingSelector(ctx, m.index, sector, stores.FTCache|stores.FTSealed, false)
-	if err != nil {
-		return xerrors.Errorf("creating path selector: %w", err)
-	}
+	selector := newExistingSelector(m.index, sector, stores.FTCache|stores.FTSealed, false)
 
-	err = m.sched.Schedule(ctx, sector, sealtasks.TTFinalize, selector,
+	err := m.sched.Schedule(ctx, sector, sealtasks.TTFinalize, selector,
 		schedFetch(sector, stores.FTCache|stores.FTSealed|unsealed, stores.PathSealing, stores.AcquireMove),
 		func(ctx context.Context, w Worker) error {
 			return w.FinalizeSector(ctx, sector, keepUnsealed)
@@ -416,11 +424,7 @@ func (m *Manager) FinalizeSector(ctx context.Context, sector abi.SectorID, keepU
 		return err
 	}
 
-	fetchSel, err := newAllocSelector(ctx, m.index, stores.FTCache|stores.FTSealed, stores.PathStorage)
-	if err != nil {
-		return xerrors.Errorf("creating fetchSel: %w", err)
-	}
-
+	fetchSel := newAllocSelector(m.index, stores.FTCache|stores.FTSealed, stores.PathStorage)
 	moveUnsealed := unsealed
 	{
 		if len(keepUnsealed) == 0 {
@@ -441,7 +445,8 @@ func (m *Manager) FinalizeSector(ctx context.Context, sector abi.SectorID, keepU
 }
 
 func (m *Manager) ReleaseUnsealed(ctx context.Context, sector abi.SectorID, safeToFree []storage.Range) error {
-	return xerrors.Errorf("implement me")
+	log.Warnw("ReleaseUnsealed todo")
+	return nil
 }
 
 func (m *Manager) Remove(ctx context.Context, sector abi.SectorID) error {
@@ -464,10 +469,7 @@ func (m *Manager) Remove(ctx context.Context, sector abi.SectorID) error {
 		}
 	}
 
-	selector, err := newExistingSelector(ctx, m.index, sector, stores.FTCache|stores.FTSealed, false)
-	if err != nil {
-		return xerrors.Errorf("creating selector: %w", err)
-	}
+	selector := newExistingSelector(m.index, sector, stores.FTCache|stores.FTSealed, false)
 
 	return m.sched.Schedule(ctx, sector, sealtasks.TTFinalize, selector,
 		schedFetch(sector, stores.FTCache|stores.FTSealed|unsealed, stores.PathStorage, stores.AcquireMove),
@@ -490,12 +492,16 @@ func (m *Manager) StorageLocal(ctx context.Context) (map[stores.ID]string, error
 	return out, nil
 }
 
-func (m *Manager) FsStat(ctx context.Context, id stores.ID) (stores.FsStat, error) {
+func (m *Manager) FsStat(ctx context.Context, id stores.ID) (fsutil.FsStat, error) {
 	return m.storage.FsStat(ctx, id)
 }
 
-func (m *Manager) Close() error {
-	return m.sched.Close()
+func (m *Manager) SchedDiag(ctx context.Context) (interface{}, error) {
+	return m.sched.Info(ctx)
+}
+
+func (m *Manager) Close(ctx context.Context) error {
+	return m.sched.Close(ctx)
 }
 
 var _ SectorManager = &Manager{}
diff --git a/manager_test.go b/manager_test.go
index ae318b487..10e6a5020 100644
--- a/manager_test.go
+++ b/manager_test.go
@@ -5,6 +5,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"github.com/filecoin-project/sector-storage/sealtasks"
 	logging "github.com/ipfs/go-log"
 	"io/ioutil"
@@ -22,8 +23,16 @@ import (
 	"github.com/filecoin-project/sector-storage/stores"
 )
 
+func init() {
+	logging.SetAllLoggers(logging.LevelDebug)
+}
+
 type testStorage stores.StorageConfig
 
+func (t testStorage) DiskUsage(path string) (int64, error) {
+	return 1, nil // close enough
+}
+
 func newTestStorage(t *testing.T) *testStorage {
 	tp, err := ioutil.TempDir(os.TempDir(), "sector-storage-test-")
 	require.NoError(t, err)
@@ -65,8 +74,8 @@ func (t *testStorage) SetStorage(f func(*stores.StorageConfig)) error {
 	return nil
 }
 
-func (t *testStorage) Stat(path string) (stores.FsStat, error) {
-	return stores.Stat(path)
+func (t *testStorage) Stat(path string) (fsutil.FsStat, error) {
+	return fsutil.Statfs(path)
 }
 
 var _ stores.LocalStorage = &testStorage{}
@@ -86,7 +95,7 @@ func newTestMgr(ctx context.Context, t *testing.T) (*Manager, *stores.Local, *st
 	prover, err := ffiwrapper.New(&readonlyProvider{stor: lstor}, cfg)
 	require.NoError(t, err)
 
-	stor := stores.NewRemote(lstor, si, nil)
+	stor := stores.NewRemote(lstor, si, nil, 6000)
 
 	m := &Manager{
 		scfg: cfg,
diff --git a/mock/mock.go b/mock/mock.go
index cbc3a1f99..6eb71cd6b 100644
--- a/mock/mock.go
+++ b/mock/mock.go
@@ -5,7 +5,6 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"math"
 	"math/rand"
 	"sync"
 
@@ -34,14 +33,22 @@ type SectorMgr struct {
 
 type mockVerif struct{}
 
-func NewMockSectorMgr(ssize abi.SectorSize) *SectorMgr {
+func NewMockSectorMgr(ssize abi.SectorSize, genesisSectors []abi.SectorID) *SectorMgr {
 	rt, err := ffiwrapper.SealProofTypeFromSectorSize(ssize)
 	if err != nil {
 		panic(err)
 	}
 
+	sectors := make(map[abi.SectorID]*sectorState)
+	for _, sid := range genesisSectors {
+		sectors[sid] = &sectorState{
+			failed: false,
+			state:  stateCommit,
+		}
+	}
+
 	return &SectorMgr{
-		sectors:      make(map[abi.SectorID]*sectorState),
+		sectors:      sectors,
 		pieces:       map[cid.Cid][]byte{},
 		sectorSize:   ssize,
 		nextSectorID: 5,
@@ -161,7 +168,7 @@ func (mgr *SectorMgr) SealPreCommit1(ctx context.Context, sid abi.SectorID, tick
 		return nil, err
 	}
 
-	cc, _, err := commcid.CIDToCommitment(commd)
+	_, _, cc, err := commcid.CIDToCommitment(commd)
 	if err != nil {
 		panic(err)
 	}
@@ -175,14 +182,14 @@ func (mgr *SectorMgr) SealPreCommit2(ctx context.Context, sid abi.SectorID, phas
 	db := []byte(string(phase1Out))
 	db[0] ^= 'd'
 
-	d := commcid.DataCommitmentV1ToCID(db)
+	d, _ := commcid.DataCommitmentV1ToCID(db)
 
 	commr := make([]byte, 32)
 	for i := range db {
 		commr[32-(i+1)] = db[i]
 	}
 
-	commR := commcid.ReplicaCommitmentV1ToCID(commr)
+	commR, _ := commcid.ReplicaCommitmentV1ToCID(commr)
 
 	return storage.SectorCids{
 		Unsealed: d,
@@ -229,7 +236,7 @@ func (mgr *SectorMgr) SealCommit2(ctx context.Context, sid abi.SectorID, phase1O
 
 // Test Instrumentation Methods
 
-func (mgr *SectorMgr) FailSector(sid abi.SectorID) error {
+func (mgr *SectorMgr) MarkFailed(sid abi.SectorID, failed bool) error {
 	mgr.lk.Lock()
 	defer mgr.lk.Unlock()
 	ss, ok := mgr.sectors[sid]
@@ -237,7 +244,7 @@ func (mgr *SectorMgr) FailSector(sid abi.SectorID) error {
 		return fmt.Errorf("no such sector in storage")
 	}
 
-	ss.failed = true
+	ss.failed = failed
 	return nil
 }
 
@@ -258,27 +265,57 @@ func AddOpFinish(ctx context.Context) (context.Context, func()) {
 }
 
 func (mgr *SectorMgr) GenerateWinningPoSt(ctx context.Context, minerID abi.ActorID, sectorInfo []abi.SectorInfo, randomness abi.PoStRandomness) ([]abi.PoStProof, error) {
-	return generateFakePoSt(sectorInfo, abi.RegisteredSealProof.RegisteredWinningPoStProof), nil
+	return generateFakePoSt(sectorInfo, abi.RegisteredSealProof.RegisteredWinningPoStProof, randomness), nil
 }
 
 func (mgr *SectorMgr) GenerateWindowPoSt(ctx context.Context, minerID abi.ActorID, sectorInfo []abi.SectorInfo, randomness abi.PoStRandomness) ([]abi.PoStProof, []abi.SectorID, error) {
-	return generateFakePoSt(sectorInfo, abi.RegisteredSealProof.RegisteredWindowPoStProof), nil, nil
+	si := make([]abi.SectorInfo, 0, len(sectorInfo))
+	var skipped []abi.SectorID
+
+	for _, info := range sectorInfo {
+		sid := abi.SectorID{
+			Miner:  minerID,
+			Number: info.SectorNumber,
+		}
+
+		_, found := mgr.sectors[sid]
+
+		if found && !mgr.sectors[sid].failed {
+			si = append(si, info)
+		} else {
+			skipped = append(skipped, sid)
+		}
+	}
+
+	return generateFakePoSt(si, abi.RegisteredSealProof.RegisteredWindowPoStProof, randomness), skipped, nil
 }
 
-func generateFakePoSt(sectorInfo []abi.SectorInfo, rpt func(abi.RegisteredSealProof) (abi.RegisteredPoStProof, error)) []abi.PoStProof {
-	se, err := sectorInfo[0].SealProof.WindowPoStPartitionSectors()
+func generateFakePoSt(sectorInfo []abi.SectorInfo, rpt func(abi.RegisteredSealProof) (abi.RegisteredPoStProof, error), randomness abi.PoStRandomness) []abi.PoStProof {
+	sectors := abi.NewBitField()
+	for _, info := range sectorInfo {
+		sectors.Set(uint64(info.SectorNumber))
+	}
+
+	wp, err := rpt(sectorInfo[0].SealProof)
 	if err != nil {
 		panic(err)
 	}
-	wp, err := rpt(sectorInfo[0].SealProof)
+
+	var proofBuf bytes.Buffer
+
+	_, err = proofBuf.Write(randomness)
 	if err != nil {
 		panic(err)
 	}
 
+	if err := sectors.MarshalCBOR(&proofBuf); err != nil {
+		panic(err)
+	}
+
 	return []abi.PoStProof{
 		{
 			PoStProof:  wp,
-			ProofBytes: make([]byte, 192*int(math.Ceil(float64(len(sectorInfo))/float64(se)))),
+			ProofBytes: proofBuf.Bytes(),
 		},
 	}
 }
@@ -320,7 +357,7 @@ func (mgr *SectorMgr) FinalizeSector(context.Context, abi.SectorID, []storage.Ra
 }
 
 func (mgr *SectorMgr) ReleaseUnsealed(ctx context.Context, sector abi.SectorID, safeToFree []storage.Range) error {
-	panic("implement me")
+	return nil
 }
 
 func (mgr *SectorMgr) Remove(ctx context.Context, sector abi.SectorID) error {
@@ -335,8 +372,18 @@ func (mgr *SectorMgr) Remove(ctx context.Context, sector abi.SectorID) error {
 	return nil
 }
 
-func (mgr *SectorMgr) CheckProvable(context.Context, abi.RegisteredSealProof, []abi.SectorID) ([]abi.SectorID, error) {
-	return nil, nil
+func (mgr *SectorMgr) CheckProvable(ctx context.Context, spt abi.RegisteredSealProof, ids []abi.SectorID) ([]abi.SectorID, error) {
+	var bad []abi.SectorID
+
+	for _, sid := range ids {
+		_, found := mgr.sectors[sid]
+
+		if !found || mgr.sectors[sid].failed {
+			bad = append(bad, sid)
+		}
+	}
+
+	return bad, nil
 }
 
 func (m mockVerif) VerifySeal(svi abi.SealVerifyInfo) (bool, error) {
@@ -358,6 +405,42 @@ func (m mockVerif) VerifyWinningPoSt(ctx context.Context, info abi.WinningPoStVe
 }
 
 func (m mockVerif) VerifyWindowPoSt(ctx context.Context, info abi.WindowPoStVerifyInfo) (bool, error) {
+	if len(info.Proofs) != 1 {
+		return false, xerrors.Errorf("expected 1 proof entry")
+	}
+
+	proof := info.Proofs[0]
+
+	if !bytes.Equal(proof.ProofBytes[:len(info.Randomness)], info.Randomness) {
+		return false, xerrors.Errorf("bad randomness")
+	}
+
+	sectors := abi.NewBitField()
+	if err := sectors.UnmarshalCBOR(bytes.NewReader(proof.ProofBytes[len(info.Randomness):])); err != nil {
+		return false, xerrors.Errorf("unmarshaling sectors bitfield from \"proof\": %w", err)
+	}
+
+	challenged := abi.NewBitField()
+	for _, sector := range info.ChallengedSectors {
+		challenged.Set(uint64(sector.SectorNumber))
+	}
+
+	{
+		b1, err := sectors.MarshalJSON()
+		if err != nil {
+			return false, err
+		}
+
+		b2, err := challenged.MarshalJSON()
+		if err != nil {
+			return false, err
+		}
+
+		if !bytes.Equal(b1, b2) {
+			return false, xerrors.Errorf("proven and challenged sector sets didn't match: %s != !s", string(b1), string(b2))
+		}
+	}
+
 	return true, nil
 }
 
diff --git a/mock/mock_test.go b/mock/mock_test.go
index 5f4b9c428..c7d43e8b9 100644
--- a/mock/mock_test.go
+++ b/mock/mock_test.go
@@ -9,7 +9,7 @@ import (
 )
 
 func TestOpFinish(t *testing.T) {
-	sb := NewMockSectorMgr(2048)
+	sb := NewMockSectorMgr(2048, nil)
 
 	sid, pieces, err := sb.StageFakeData(123)
 	if err != nil {
diff --git a/request_queue.go b/request_queue.go
index 0d35e9f1d..85d3abf46 100644
--- a/request_queue.go
+++ b/request_queue.go
@@ -1,6 +1,6 @@
 package sectorstorage
 
-import "container/heap"
+import "sort"
 
 type requestQueue []*workerRequest
 
@@ -24,21 +24,22 @@ func (q requestQueue) Swap(i, j int) {
 	q[j].index = j
 }
 
-func (q *requestQueue) Push(x interface{}) {
+func (q *requestQueue) Push(x *workerRequest) {
 	n := len(*q)
-	item := x.(*workerRequest)
+	item := x
 	item.index = n
 	*q = append(*q, item)
+	sort.Sort(q)
 }
 
-func (q *requestQueue) Pop() interface{} {
+func (q *requestQueue) Remove(i int) *workerRequest {
 	old := *q
 	n := len(old)
-	item := old[n-1]
-	old[n-1] = nil  // avoid memory leak
-	item.index = -1 // for safety
+	item := old[i]
+	old[i] = old[n-1]
+	old[n-1] = nil
+	item.index = -1
 	*q = old[0 : n-1]
+	sort.Sort(q)
 	return item
 }
-
-var _ heap.Interface = &requestQueue{}
diff --git a/request_queue_test.go b/request_queue_test.go
index 9bf231e39..cb4a5d5dd 100644
--- a/request_queue_test.go
+++ b/request_queue_test.go
@@ -1,7 +1,7 @@
 package sectorstorage
 
 import (
-	"container/heap"
+	"fmt"
 	"testing"
 
 	"github.com/filecoin-project/sector-storage/sealtasks"
@@ -10,19 +10,51 @@ import (
 func TestRequestQueue(t *testing.T) {
 	rq := &requestQueue{}
 
-	heap.Push(rq, &workerRequest{taskType: sealtasks.TTAddPiece})
-	heap.Push(rq, &workerRequest{taskType: sealtasks.TTPreCommit1})
-	heap.Push(rq, &workerRequest{taskType: sealtasks.TTPreCommit2})
-	heap.Push(rq, &workerRequest{taskType: sealtasks.TTPreCommit1})
-	heap.Push(rq, &workerRequest{taskType: sealtasks.TTAddPiece})
+	rq.Push(&workerRequest{taskType: sealtasks.TTAddPiece})
+	rq.Push(&workerRequest{taskType: sealtasks.TTPreCommit1})
+	rq.Push(&workerRequest{taskType: sealtasks.TTPreCommit2})
+	rq.Push(&workerRequest{taskType: sealtasks.TTPreCommit1})
+	rq.Push(&workerRequest{taskType: sealtasks.TTAddPiece})
 
-	pt := heap.Pop(rq).(*workerRequest)
+	dump := func(s string) {
+		fmt.Println("---")
+		fmt.Println(s)
+
+		for sqi := 0; sqi < rq.Len(); sqi++ {
+			task := (*rq)[sqi]
+			fmt.Println(sqi, task.taskType)
+		}
+	}
+
+	dump("start")
+
+	pt := rq.Remove(0)
+
+	dump("pop 1")
 
 	if pt.taskType != sealtasks.TTPreCommit2 {
 		t.Error("expected precommit2, got", pt.taskType)
 	}
 
-	pt = heap.Pop(rq).(*workerRequest)
+	pt = rq.Remove(0)
+
+	dump("pop 2")
+
+	if pt.taskType != sealtasks.TTPreCommit1 {
+		t.Error("expected precommit1, got", pt.taskType)
+	}
+
+	pt = rq.Remove(1)
+
+	dump("pop 3")
+
+	if pt.taskType != sealtasks.TTAddPiece {
+		t.Error("expected addpiece, got", pt.taskType)
+	}
+
+	pt = rq.Remove(0)
+
+	dump("pop 4")
 
 	if pt.taskType != sealtasks.TTPreCommit1 {
 		t.Error("expected precommit1, got", pt.taskType)
diff --git a/sched.go b/sched.go
index 9fddd7bd9..e8eda4834 100644
--- a/sched.go
+++ b/sched.go
@@ -1,13 +1,13 @@
 package sectorstorage
 
 import (
-	"container/heap"
 	"context"
+	"fmt"
+	"math/rand"
 	"sort"
 	"sync"
 	"time"
 
-	"github.com/hashicorp/go-multierror"
 	"golang.org/x/xerrors"
 
 	"github.com/filecoin-project/specs-actors/actors/abi"
@@ -20,6 +20,11 @@ type schedPrioCtxKey int
 
 var SchedPriorityKey schedPrioCtxKey
 var DefaultSchedPriority = 0
+var SelectorTimeout = 5 * time.Second
+
+var (
+	SchedWindows = 2
+)
 
 func getPriority(ctx context.Context) int {
 	sp := ctx.Value(SchedPriorityKey)
@@ -47,7 +52,7 @@ type WorkerSelector interface {
 type scheduler struct {
 	spt abi.RegisteredSealProof
 
-	workersLk  sync.Mutex
+	workersLk  sync.RWMutex
 	nextWorker WorkerID
 	workers    map[WorkerID]*workerHandle
 
@@ -56,11 +61,77 @@ type scheduler struct {
 	watchClosing  chan WorkerID
 	workerClosing chan WorkerID
 
-	schedule   chan *workerRequest
-	workerFree chan WorkerID
-	closing    chan struct{}
+	schedule       chan *workerRequest
+	windowRequests chan *schedWindowRequest
 
-	schedQueue *requestQueue
+	// owned by the sh.runSched goroutine
+	schedQueue  *requestQueue
+	openWindows []*schedWindowRequest
+
+	info chan func(interface{})
+
+	closing  chan struct{}
+	closed   chan struct{}
+	testSync chan struct{} // used for testing
+}
+
+type workerHandle struct {
+	w Worker
+
+	info storiface.WorkerInfo
+
+	preparing *activeResources
+	active    *activeResources
+
+	lk sync.Mutex
+
+	// stats / tracking
+	wt *workTracker
+
+	// for sync manager goroutine closing
+	cleanupStarted bool
+	closedMgr      chan struct{}
+	closingMgr     chan struct{}
+}
+
+type schedWindowRequest struct {
+	worker WorkerID
+
+	done chan *schedWindow
+}
+
+type schedWindow struct {
+	allocated activeResources
+	todo      []*workerRequest
+}
+
+type activeResources struct {
+	memUsedMin uint64
+	memUsedMax uint64
+	gpuUsed    bool
+	cpuUse     uint64
+
+	cond *sync.Cond
+}
+
+type workerRequest struct {
+	sector   abi.SectorID
+	taskType sealtasks.TaskType
+	priority int // larger values more important
+	sel      WorkerSelector
+
+	prepare WorkerAction
+	work    WorkerAction
+
+	index int // The index of the item in the heap.
+
+	indexHeap int
+	ret       chan<- workerResponse
+	ctx       context.Context
+}
+
+type workerResponse struct {
+	err error
 }
 
 func newScheduler(spt abi.RegisteredSealProof) *scheduler {
@@ -75,11 +146,15 @@ func newScheduler(spt abi.RegisteredSealProof) *scheduler {
 		watchClosing:  make(chan WorkerID),
 		workerClosing: make(chan WorkerID),
 
-		schedule:   make(chan *workerRequest),
-		workerFree: make(chan WorkerID),
-		closing:    make(chan struct{}),
+		schedule:       make(chan *workerRequest),
+		windowRequests: make(chan *schedWindowRequest),
 
 		schedQueue: &requestQueue{},
+
+		info: make(chan func(interface{})),
+
+		closing: make(chan struct{}),
+		closed:  make(chan struct{}),
 	}
 }
 
@@ -115,25 +190,6 @@ func (sh *scheduler) Schedule(ctx context.Context, sector abi.SectorID, taskType
 	}
 }
 
-type workerRequest struct {
-	sector   abi.SectorID
-	taskType sealtasks.TaskType
-	priority int // larger values more important
-	sel      WorkerSelector
-
-	prepare WorkerAction
-	work    WorkerAction
-
-	index int // The index of the item in the heap.
-
-	ret chan<- workerResponse
-	ctx context.Context
-}
-
-type workerResponse struct {
-	err error
-}
-
 func (r *workerRequest) respond(err error) {
 	select {
 	case r.ret <- workerResponse{err: err}:
@@ -142,46 +198,44 @@ func (r *workerRequest) respond(err error) {
 	}
 }
 
-type activeResources struct {
-	memUsedMin uint64
-	memUsedMax uint64
-	gpuUsed    bool
-	cpuUse     uint64
-
-	cond *sync.Cond
+type SchedDiagRequestInfo struct {
+	Sector   abi.SectorID
+	TaskType sealtasks.TaskType
+	Priority int
 }
 
-type workerHandle struct {
-	w Worker
-
-	info storiface.WorkerInfo
-
-	preparing *activeResources
-	active    *activeResources
+type SchedDiagInfo struct {
+	Requests    []SchedDiagRequestInfo
+	OpenWindows []WorkerID
 }
 
 func (sh *scheduler) runSched() {
+	defer close(sh.closed)
+
 	go sh.runWorkerWatcher()
 
 	for {
 		select {
 		case w := <-sh.newWorkers:
-			sh.schedNewWorker(w)
-		case wid := <-sh.workerClosing:
-			sh.schedDropWorker(wid)
-		case req := <-sh.schedule:
-			scheduled, err := sh.maybeSchedRequest(req)
-			if err != nil {
-				req.respond(err)
-				continue
-			}
-			if scheduled {
-				continue
-			}
+			sh.newWorker(w)
+
+		case wid := <-sh.workerClosing:
+			sh.dropWorker(wid)
+
+		case req := <-sh.schedule:
+			sh.schedQueue.Push(req)
+			sh.trySched()
+
+			if sh.testSync != nil {
+				sh.testSync <- struct{}{}
+			}
+		case req := <-sh.windowRequests:
+			sh.openWindows = append(sh.openWindows, req)
+			sh.trySched()
+
+		case ireq := <-sh.info:
+			ireq(sh.diag())
 
-			heap.Push(sh.schedQueue, req)
-		case wid := <-sh.workerFree:
-			sh.onWorkerFreed(wid)
 		case <-sh.closing:
 			sh.schedClose()
 			return
@@ -189,119 +243,317 @@ func (sh *scheduler) runSched() {
 	}
 }
 
-func (sh *scheduler) onWorkerFreed(wid WorkerID) {
-	sh.workersLk.Lock()
-	w, ok := sh.workers[wid]
-	sh.workersLk.Unlock()
-	if !ok {
-		log.Warnf("onWorkerFreed on invalid worker %d", wid)
+func (sh *scheduler) diag() SchedDiagInfo {
+	var out SchedDiagInfo
+
+	for sqi := 0; sqi < sh.schedQueue.Len(); sqi++ {
+		task := (*sh.schedQueue)[sqi]
+
+		out.Requests = append(out.Requests, SchedDiagRequestInfo{
+			Sector:   task.sector,
+			TaskType: task.taskType,
+			Priority: task.priority,
+		})
+	}
+
+	for _, window := range sh.openWindows {
+		out.OpenWindows = append(out.OpenWindows, window.worker)
+	}
+
+	return out
+}
+
+func (sh *scheduler) trySched() {
+	/*
+		This assigns tasks to workers based on:
+		- Task priority (achieved by handling sh.schedQueue in order, since it's already sorted by priority)
+		- Worker resource availability
+		- Task-specified worker preference (acceptableWindows array below sorted by this preference)
+		- Window request age
+
+		1. For each task in the schedQueue find windows which can handle them
+		1.1. Create list of windows capable of handling a task
+		1.2. Sort windows according to task selector preferences
+		2. Going through schedQueue again, assign task to first acceptable window
+		   with resources available
+		3. Submit windows with scheduled tasks to workers
+
+	*/
+
+	windows := make([]schedWindow, len(sh.openWindows))
+	acceptableWindows := make([][]int, sh.schedQueue.Len())
+
+	log.Debugf("SCHED %d queued; %d open windows", sh.schedQueue.Len(), len(windows))
+
+	sh.workersLk.RLock()
+	defer sh.workersLk.RUnlock()
+
+	// Step 1
+	for sqi := 0; sqi < sh.schedQueue.Len(); sqi++ {
+		task := (*sh.schedQueue)[sqi]
+		needRes := ResourceTable[task.taskType][sh.spt]
+
+		task.indexHeap = sqi
+		for wnd, windowRequest := range sh.openWindows {
+			worker := sh.workers[windowRequest.worker]
+
+			// TODO: allow bigger windows
+			if !windows[wnd].allocated.canHandleRequest(needRes, windowRequest.worker, worker.info.Resources) {
+				continue
+			}
+
+			rpcCtx, cancel := context.WithTimeout(task.ctx, SelectorTimeout)
+			ok, err := task.sel.Ok(rpcCtx, task.taskType, sh.spt, worker)
+			cancel()
+			if err != nil {
+				log.Errorf("trySched(1) req.sel.Ok error: %+v", err)
+				continue
+			}
+
+			if !ok {
+				continue
+			}
+
+			acceptableWindows[sqi] = append(acceptableWindows[sqi], wnd)
+		}
+
+		if len(acceptableWindows[sqi]) == 0 {
+			continue
+		}
+
+		// Pick best worker (shuffle in case some workers are equally as good)
+		rand.Shuffle(len(acceptableWindows[sqi]), func(i, j int) {
+			acceptableWindows[sqi][i], acceptableWindows[sqi][j] = acceptableWindows[sqi][j], acceptableWindows[sqi][i]
+		})
+		sort.SliceStable(acceptableWindows[sqi], func(i, j int) bool {
+			wii := sh.openWindows[acceptableWindows[sqi][i]].worker
+			wji := sh.openWindows[acceptableWindows[sqi][j]].worker
+
+			if wii == wji {
+				// for the same worker prefer older windows
+				return acceptableWindows[sqi][i] < acceptableWindows[sqi][j]
+			}
+
+			wi := sh.workers[wii]
+			wj := sh.workers[wji]
+
+			rpcCtx, cancel := context.WithTimeout(task.ctx, SelectorTimeout)
+			defer cancel()
+
+			r, err := task.sel.Cmp(rpcCtx, task.taskType, wi, wj)
+			if err != nil {
+				log.Error("selecting best worker: %s", err)
+			}
+			return r
+		})
+	}
+
+	log.Debugf("SCHED windows: %+v", windows)
+	log.Debugf("SCHED Acceptable win: %+v", acceptableWindows)
+
+	// Step 2
+	scheduled := 0
+
+	for sqi := 0; sqi < sh.schedQueue.Len(); sqi++ {
+		task := (*sh.schedQueue)[sqi]
+		needRes := ResourceTable[task.taskType][sh.spt]
+
+		selectedWindow := -1
+		for _, wnd := range acceptableWindows[task.indexHeap] {
+			wid := sh.openWindows[wnd].worker
+			wr := sh.workers[wid].info.Resources
+
+			log.Debugf("SCHED try assign sqi:%d sector %d to window %d", sqi, task.sector.Number, wnd)
+
+			// TODO: allow bigger windows
+			if !windows[wnd].allocated.canHandleRequest(needRes, wid, wr) {
+				continue
+			}
+
+			log.Debugf("SCHED ASSIGNED sqi:%d sector %d to window %d", sqi, task.sector.Number, wnd)
+
+			windows[wnd].allocated.add(wr, needRes)
+
+			selectedWindow = wnd
+			break
+		}
+
+		if selectedWindow < 0 {
+			// all windows full
+			continue
+		}
+
+		windows[selectedWindow].todo = append(windows[selectedWindow].todo, task)
+
+		sh.schedQueue.Remove(sqi)
+		sqi--
+		scheduled++
+	}
+
+	// Step 3
+
+	if scheduled == 0 {
 		return
 	}
 
-	for i := 0; i < sh.schedQueue.Len(); i++ {
-		req := (*sh.schedQueue)[i]
-
-		ok, err := req.sel.Ok(req.ctx, req.taskType, sh.spt, w)
-		if err != nil {
-			log.Errorf("onWorkerFreed req.sel.Ok error: %+v", err)
+	scheduledWindows := map[int]struct{}{}
+	for wnd, window := range windows {
+		if len(window.todo) == 0 {
+			// Nothing scheduled here, keep the window open
 			continue
 		}
 
-		if !ok {
-			continue
-		}
+		scheduledWindows[wnd] = struct{}{}
 
-		scheduled, err := sh.maybeSchedRequest(req)
-		if err != nil {
-			req.respond(err)
-			continue
-		}
-
-		if scheduled {
-			heap.Remove(sh.schedQueue, i)
-			i--
-			continue
+		window := window // copy
+		select {
+		case sh.openWindows[wnd].done <- &window:
+		default:
+			log.Error("expected sh.openWindows[wnd].done to be buffered")
 		}
 	}
+
+	// Rewrite sh.openWindows array, removing scheduled windows
+	newOpenWindows := make([]*schedWindowRequest, 0, len(sh.openWindows)-len(scheduledWindows))
+	for wnd, window := range sh.openWindows {
+		if _, scheduled := scheduledWindows[wnd]; scheduled {
+			// keep unscheduled windows open
+			continue
+		}
+
+		newOpenWindows = append(newOpenWindows, window)
+	}
+
+	sh.openWindows = newOpenWindows
 }
 
-var selectorTimeout = 5 * time.Second
-
-func (sh *scheduler) maybeSchedRequest(req *workerRequest) (bool, error) {
-	sh.workersLk.Lock()
-	defer sh.workersLk.Unlock()
-
-	tried := 0
-	var acceptable []WorkerID
-
-	needRes := ResourceTable[req.taskType][sh.spt]
-
-	for wid, worker := range sh.workers {
-		rpcCtx, cancel := context.WithTimeout(req.ctx, selectorTimeout)
-		ok, err := req.sel.Ok(rpcCtx, req.taskType, sh.spt, worker)
-		cancel()
-
-		if err != nil {
-			return false, err
-		}
-
-		if !ok {
-			continue
-		}
-		tried++
-
-		if !canHandleRequest(needRes, wid, worker.info.Resources, worker.preparing) {
-			continue
-		}
-
-		acceptable = append(acceptable, wid)
-	}
-
-	if len(acceptable) > 0 {
-		{
-			var serr error
-
-			sort.SliceStable(acceptable, func(i, j int) bool {
-				rpcCtx, cancel := context.WithTimeout(req.ctx, selectorTimeout)
-				defer cancel()
-				r, err := req.sel.Cmp(rpcCtx, req.taskType, sh.workers[acceptable[i]], sh.workers[acceptable[j]])
-
-				if err != nil {
-					serr = multierror.Append(serr, err)
-				}
-				return r
-			})
-
-			if serr != nil {
-				return false, xerrors.Errorf("error(s) selecting best worker: %w", serr)
-			}
-		}
-
-		return true, sh.assignWorker(acceptable[0], sh.workers[acceptable[0]], req)
-	}
-
-	if tried == 0 {
-		return false, xerrors.New("maybeSchedRequest didn't find any good workers")
-	}
-
-	return false, nil // put in waiting queue
-}
-
-func (sh *scheduler) assignWorker(wid WorkerID, w *workerHandle, req *workerRequest) error {
-	needRes := ResourceTable[req.taskType][sh.spt]
-
-	w.preparing.add(w.info.Resources, needRes)
+func (sh *scheduler) runWorker(wid WorkerID) {
+	var ready sync.WaitGroup
+	ready.Add(1)
+	defer ready.Wait()
 
 	go func() {
-		err := req.prepare(req.ctx, w.w)
+		sh.workersLk.RLock()
+		worker, found := sh.workers[wid]
+		sh.workersLk.RUnlock()
+
+		ready.Done()
+
+		if !found {
+			panic(fmt.Sprintf("worker %d not found", wid))
+		}
+
+		defer close(worker.closedMgr)
+
+		scheduledWindows := make(chan *schedWindow, SchedWindows)
+		taskDone := make(chan struct{}, 1)
+		windowsRequested := 0
+
+		var activeWindows []*schedWindow
+
+		ctx, cancel := context.WithCancel(context.TODO())
+		defer cancel()
+
+		workerClosing, err := worker.w.Closing(ctx)
+		if err != nil {
+			return
+		}
+
+		defer func() {
+			log.Warnw("Worker closing", "workerid", wid)
+
+			// TODO: close / return all queued tasks
+		}()
+
+		for {
+			// ask for more windows if we need them
+			for ; windowsRequested < SchedWindows; windowsRequested++ {
+				select {
+				case sh.windowRequests <- &schedWindowRequest{
+					worker: wid,
+					done:   scheduledWindows,
+				}:
+				case <-sh.closing:
+					return
+				case <-workerClosing:
+					return
+				case <-worker.closingMgr:
+					return
+				}
+			}
+
+			select {
+			case w := <-scheduledWindows:
+				activeWindows = append(activeWindows, w)
+			case <-taskDone:
+				log.Debugw("task done", "workerid", wid)
+			case <-sh.closing:
+				return
+			case <-workerClosing:
+				return
+			case <-worker.closingMgr:
+				return
+			}
+
+		assignLoop:
+			// process windows in order
+			for len(activeWindows) > 0 {
+				// process tasks within a window in order
+				for len(activeWindows[0].todo) > 0 {
+					todo := activeWindows[0].todo[0]
+					needRes := ResourceTable[todo.taskType][sh.spt]
+
+					sh.workersLk.RLock()
+					worker.lk.Lock()
+					ok := worker.preparing.canHandleRequest(needRes, wid, worker.info.Resources)
+					worker.lk.Unlock()
+
+					if !ok {
+						sh.workersLk.RUnlock()
+						break assignLoop
+					}
+
+					log.Debugf("assign worker sector %d", todo.sector.Number)
+					err := sh.assignWorker(taskDone, wid, worker, todo)
+					sh.workersLk.RUnlock()
+
+					if err != nil {
+						log.Error("assignWorker error: %+v", err)
+						go todo.respond(xerrors.Errorf("assignWorker error: %w", err))
+					}
+
+					activeWindows[0].todo = activeWindows[0].todo[1:]
+				}
+
+				copy(activeWindows, activeWindows[1:])
+				activeWindows[len(activeWindows)-1] = nil
+				activeWindows = activeWindows[:len(activeWindows)-1]
+
+				windowsRequested--
+			}
+		}
+	}()
+}
+
+func (sh *scheduler) assignWorker(taskDone chan struct{}, wid WorkerID, w *workerHandle, req *workerRequest) error {
+	needRes := ResourceTable[req.taskType][sh.spt]
+
+	w.lk.Lock()
+	w.preparing.add(w.info.Resources, needRes)
+	w.lk.Unlock()
+
+	go func() {
+		err := req.prepare(req.ctx, w.wt.worker(w.w))
 		sh.workersLk.Lock()
 
 		if err != nil {
+			w.lk.Lock()
 			w.preparing.free(w.info.Resources, needRes)
+			w.lk.Unlock()
 			sh.workersLk.Unlock()
 
 			select {
-			case sh.workerFree <- wid:
+			case taskDone <- struct{}{}:
 			case <-sh.closing:
 				log.Warnf("scheduler closed while sending response (prepare error: %+v)", err)
 			}
@@ -317,16 +569,18 @@ func (sh *scheduler) assignWorker(wid WorkerID, w *workerHandle, req *workerRequ
 		}
 
 		err = w.active.withResources(wid, w.info.Resources, needRes, &sh.workersLk, func() error {
+			w.lk.Lock()
 			w.preparing.free(w.info.Resources, needRes)
+			w.lk.Unlock()
 			sh.workersLk.Unlock()
 			defer sh.workersLk.Lock() // we MUST return locked from this function
 
 			select {
-			case sh.workerFree <- wid:
+			case taskDone <- struct{}{}:
 			case <-sh.closing:
 			}
 
-			err = req.work(req.ctx, w.w)
+			err = req.work(req.ctx, w.wt.worker(w.w))
 
 			select {
 			case req.ret <- workerResponse{err: err}:
@@ -350,110 +604,10 @@ func (sh *scheduler) assignWorker(wid WorkerID, w *workerHandle, req *workerRequ
 	return nil
 }
 
-func (a *activeResources) withResources(id WorkerID, wr storiface.WorkerResources, r Resources, locker sync.Locker, cb func() error) error {
-	for !canHandleRequest(r, id, wr, a) {
-		if a.cond == nil {
-			a.cond = sync.NewCond(locker)
-		}
-		a.cond.Wait()
-	}
+func (sh *scheduler) newWorker(w *workerHandle) {
+	w.closedMgr = make(chan struct{})
+	w.closingMgr = make(chan struct{})
 
-	a.add(wr, r)
-
-	err := cb()
-
-	a.free(wr, r)
-	if a.cond != nil {
-		a.cond.Broadcast()
-	}
-
-	return err
-}
-
-func (a *activeResources) add(wr storiface.WorkerResources, r Resources) {
-	a.gpuUsed = r.CanGPU
-	if r.MultiThread() {
-		a.cpuUse += wr.CPUs
-	} else {
-		a.cpuUse += uint64(r.Threads)
-	}
-
-	a.memUsedMin += r.MinMemory
-	a.memUsedMax += r.MaxMemory
-}
-
-func (a *activeResources) free(wr storiface.WorkerResources, r Resources) {
-	if r.CanGPU {
-		a.gpuUsed = false
-	}
-	if r.MultiThread() {
-		a.cpuUse -= wr.CPUs
-	} else {
-		a.cpuUse -= uint64(r.Threads)
-	}
-
-	a.memUsedMin -= r.MinMemory
-	a.memUsedMax -= r.MaxMemory
-}
-
-func canHandleRequest(needRes Resources, wid WorkerID, res storiface.WorkerResources, active *activeResources) bool {
-
-	// TODO: dedupe needRes.BaseMinMemory per task type (don't add if that task is already running)
-	minNeedMem := res.MemReserved + active.memUsedMin + needRes.MinMemory + needRes.BaseMinMemory
-	if minNeedMem > res.MemPhysical {
-		log.Debugf("sched: not scheduling on worker %d; not enough physical memory - need: %dM, have %dM", wid, minNeedMem/mib, res.MemPhysical/mib)
-		return false
-	}
-
-	maxNeedMem := res.MemReserved + active.memUsedMax + needRes.MaxMemory + needRes.BaseMinMemory
-
-	if maxNeedMem > res.MemSwap+res.MemPhysical {
-		log.Debugf("sched: not scheduling on worker %d; not enough virtual memory - need: %dM, have %dM", wid, maxNeedMem/mib, (res.MemSwap+res.MemPhysical)/mib)
-		return false
-	}
-
-	if needRes.MultiThread() {
-		if active.cpuUse > 0 {
-			log.Debugf("sched: not scheduling on worker %d; multicore process needs %d threads, %d in use, target %d", wid, res.CPUs, active.cpuUse, res.CPUs)
-			return false
-		}
-	} else {
-		if active.cpuUse+uint64(needRes.Threads) > res.CPUs {
-			log.Debugf("sched: not scheduling on worker %d; not enough threads, need %d, %d in use, target %d", wid, needRes.Threads, active.cpuUse, res.CPUs)
-			return false
-		}
-	}
-
-	if len(res.GPUs) > 0 && needRes.CanGPU {
-		if active.gpuUsed {
-			log.Debugf("sched: not scheduling on worker %d; GPU in use", wid)
-			return false
-		}
-	}
-
-	return true
-}
-
-func (a *activeResources) utilization(wr storiface.WorkerResources) float64 {
-	var max float64
-
-	cpu := float64(a.cpuUse) / float64(wr.CPUs)
-	max = cpu
-
-	memMin := float64(a.memUsedMin+wr.MemReserved) / float64(wr.MemPhysical)
-	if memMin > max {
-		max = memMin
-	}
-
-	memMax := float64(a.memUsedMax+wr.MemReserved) / float64(wr.MemPhysical+wr.MemSwap)
-	if memMax > max {
-		max = memMax
-	}
-
-	return max
-}
-
-func (sh *scheduler) schedNewWorker(w *workerHandle) {
 	sh.workersLk.Lock()
 
 	id := sh.nextWorker
@@ -462,41 +616,88 @@ func (sh *scheduler) schedNewWorker(w *workerHandle) {
 
 	sh.workersLk.Unlock()
 
+	sh.runWorker(id)
+
 	select {
 	case sh.watchClosing <- id:
 	case <-sh.closing:
 		return
 	}
-
-	sh.onWorkerFreed(id)
 }
 
-func (sh *scheduler) schedDropWorker(wid WorkerID) {
+func (sh *scheduler) dropWorker(wid WorkerID) {
 	sh.workersLk.Lock()
 	defer sh.workersLk.Unlock()
 
 	w := sh.workers[wid]
-	delete(sh.workers, wid)
 
-	go func() {
-		if err := w.w.Close(); err != nil {
-			log.Warnf("closing worker %d: %+v", err)
+	sh.workerCleanup(wid, w)
+
+	delete(sh.workers, wid)
+}
+
+func (sh *scheduler) workerCleanup(wid WorkerID, w *workerHandle) {
+	if !w.cleanupStarted {
+		close(w.closingMgr)
+	}
+	select {
+	case <-w.closedMgr:
+	case <-time.After(time.Second):
+		log.Errorf("timeout closing worker manager goroutine %d", wid)
+	}
+
+	if !w.cleanupStarted {
+		w.cleanupStarted = true
+
+		newWindows := make([]*schedWindowRequest, 0, len(sh.openWindows))
+		for _, window := range sh.openWindows {
+			if window.worker != wid {
+				newWindows = append(newWindows, window)
+			}
 		}
-	}()
+		sh.openWindows = newWindows
+
+		log.Debugf("dropWorker %d", wid)
+
+		go func() {
+			if err := w.w.Close(); err != nil {
+				log.Warnf("closing worker %d: %+v", err)
+			}
+		}()
+	}
 }
 
 func (sh *scheduler) schedClose() {
 	sh.workersLk.Lock()
 	defer sh.workersLk.Unlock()
+	log.Debugf("closing scheduler")
 
 	for i, w := range sh.workers {
-		if err := w.w.Close(); err != nil {
-			log.Errorf("closing worker %d: %+v", i, err)
-		}
+		sh.workerCleanup(i, w)
 	}
 }
 
-func (sh *scheduler) Close() error {
+func (sh *scheduler) Info(ctx context.Context) (interface{}, error) {
+	ch := make(chan interface{}, 1)
+
+	sh.info <- func(res interface{}) {
+		ch <- res
+	}
+
+	select {
+	case res := <-ch:
+		return res, nil
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+}
+
+func (sh *scheduler) Close(ctx context.Context) error {
 	close(sh.closing)
+	select {
+	case <-sh.closed:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
 	return nil
 }
diff --git a/sched_resources.go b/sched_resources.go
new file mode 100644
index 000000000..0ba9d1f66
--- /dev/null
+++ b/sched_resources.go
@@ -0,0 +1,110 @@
+package sectorstorage
+
+import (
+	"sync"
+
+	"github.com/filecoin-project/sector-storage/storiface"
+)
+
+func (a *activeResources) withResources(id WorkerID, wr storiface.WorkerResources, r Resources, locker sync.Locker, cb func() error) error {
+	for !a.canHandleRequest(r, id, wr) {
+		if a.cond == nil {
+			a.cond = sync.NewCond(locker)
+		}
+		a.cond.Wait()
+	}
+
+	a.add(wr, r)
+
+	err := cb()
+
+	a.free(wr, r)
+	if a.cond != nil {
+		a.cond.Broadcast()
+	}
+
+	return err
+}
+
+func (a *activeResources) add(wr storiface.WorkerResources, r Resources) {
+	a.gpuUsed = r.CanGPU
+	if r.MultiThread() {
+		a.cpuUse += wr.CPUs
+	} else {
+		a.cpuUse += uint64(r.Threads)
+	}
+
+	a.memUsedMin += r.MinMemory
+	a.memUsedMax += r.MaxMemory
+}
+
+func (a *activeResources) free(wr storiface.WorkerResources, r Resources) {
+	if r.CanGPU {
+		a.gpuUsed = false
+	}
+	if r.MultiThread() {
+		a.cpuUse -= wr.CPUs
+	} else {
+		a.cpuUse -= uint64(r.Threads)
+	}
+
+	a.memUsedMin -= r.MinMemory
+	a.memUsedMax -= r.MaxMemory
+}
+
+func (a *activeResources) canHandleRequest(needRes Resources, wid WorkerID, res storiface.WorkerResources) bool {
+
+	// TODO: dedupe needRes.BaseMinMemory per task type (don't add if that task is already running)
+	minNeedMem := res.MemReserved + a.memUsedMin + needRes.MinMemory + needRes.BaseMinMemory
+	if minNeedMem > res.MemPhysical {
+		log.Debugf("sched: not scheduling on worker %d; not enough physical memory - need: %dM, have %dM", wid, minNeedMem/mib, res.MemPhysical/mib)
+		return false
+	}
+
+	maxNeedMem := res.MemReserved + a.memUsedMax + needRes.MaxMemory + needRes.BaseMinMemory
+
+	if maxNeedMem > res.MemSwap+res.MemPhysical {
+		log.Debugf("sched: not scheduling on worker %d; not enough virtual memory - need: %dM, have %dM", wid, maxNeedMem/mib, (res.MemSwap+res.MemPhysical)/mib)
+		return false
+	}
+
+	if needRes.MultiThread() {
+		if a.cpuUse > 0 {
+			log.Debugf("sched: not scheduling on worker %d; multicore process needs %d threads, %d in use, target %d", wid, res.CPUs, a.cpuUse, res.CPUs)
+			return false
+		}
+	} else {
+		if a.cpuUse+uint64(needRes.Threads) > res.CPUs {
+			log.Debugf("sched: not scheduling on worker %d; not enough threads, need %d, %d in use, target %d", wid, needRes.Threads, a.cpuUse, res.CPUs)
+			return false
+		}
+	}
+
+	if len(res.GPUs) > 0 && needRes.CanGPU {
+		if a.gpuUsed {
+			log.Debugf("sched: not scheduling on worker %d; GPU in use", wid)
+			return false
+		}
+	}
+
+	return true
+}
+
+func (a *activeResources) utilization(wr storiface.WorkerResources) float64 {
+	var max float64
+
+	cpu := float64(a.cpuUse) / float64(wr.CPUs)
+	max = cpu
+
+	memMin := float64(a.memUsedMin+wr.MemReserved) / float64(wr.MemPhysical)
+	if memMin > max {
+		max = memMin
+	}
+
+	memMax := float64(a.memUsedMax+wr.MemReserved) / float64(wr.MemPhysical+wr.MemSwap)
+	if memMax > max {
+		max = memMax
+	}
+
+	return max
+}
diff --git a/sched_test.go b/sched_test.go
index d0d0e7ca9..6490e738e 100644
--- a/sched_test.go
+++ b/sched_test.go
@@ -2,9 +2,23 @@ package sectorstorage
 
 import (
 	"context"
+	"fmt"
+	"io"
+	"runtime"
+	"sync"
 	"testing"
+	"time"
 
+	"github.com/ipfs/go-cid"
 	"github.com/stretchr/testify/require"
+
+	"github.com/filecoin-project/specs-actors/actors/abi"
+
+	"github.com/filecoin-project/sector-storage/fsutil"
+	"github.com/filecoin-project/sector-storage/sealtasks"
+	"github.com/filecoin-project/sector-storage/stores"
+	"github.com/filecoin-project/sector-storage/storiface"
+	"github.com/filecoin-project/specs-storage/storage"
 )
 
 func TestWithPriority(t *testing.T) {
@@ -16,3 +30,424 @@ func TestWithPriority(t *testing.T) {
 
 	require.Equal(t, 2222, getPriority(ctx))
 }
+
+type schedTestWorker struct {
+	name      string
+	taskTypes map[sealtasks.TaskType]struct{}
+	paths     []stores.StoragePath
+
+	closed  bool
+	closing chan struct{}
+}
+
+func (s *schedTestWorker) SealPreCommit1(ctx context.Context, sector abi.SectorID, ticket abi.SealRandomness, pieces []abi.PieceInfo) (storage.PreCommit1Out, error) {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) SealPreCommit2(ctx context.Context, sector abi.SectorID, pc1o storage.PreCommit1Out) (storage.SectorCids, error) {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) SealCommit1(ctx context.Context, sector abi.SectorID, ticket abi.SealRandomness, seed abi.InteractiveSealRandomness, pieces []abi.PieceInfo, cids storage.SectorCids) (storage.Commit1Out, error) {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) SealCommit2(ctx context.Context, sector abi.SectorID, c1o storage.Commit1Out) (storage.Proof, error) {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) FinalizeSector(ctx context.Context, sector abi.SectorID, keepUnsealed []storage.Range) error {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) ReleaseUnsealed(ctx context.Context, sector abi.SectorID, safeToFree []storage.Range) error {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) Remove(ctx context.Context, sector abi.SectorID) error {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) NewSector(ctx context.Context, sector abi.SectorID) error {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) AddPiece(ctx context.Context, sector abi.SectorID, pieceSizes []abi.UnpaddedPieceSize, newPieceSize abi.UnpaddedPieceSize, pieceData storage.Data) (abi.PieceInfo, error) {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) MoveStorage(ctx context.Context, sector abi.SectorID) error {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) Fetch(ctx context.Context, id abi.SectorID, ft stores.SectorFileType, ptype stores.PathType, am stores.AcquireMode) error {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) UnsealPiece(ctx context.Context, id abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize, randomness abi.SealRandomness, cid cid.Cid) error {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) ReadPiece(ctx context.Context, writer io.Writer, id abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) (bool, error) {
+	panic("implement me")
+}
+
+func (s *schedTestWorker) TaskTypes(ctx context.Context) (map[sealtasks.TaskType]struct{}, error) {
+	return s.taskTypes, nil
+}
+
+func (s *schedTestWorker) Paths(ctx context.Context) ([]stores.StoragePath, error) {
+	return s.paths, nil
+}
+
+func (s *schedTestWorker) Info(ctx context.Context) (storiface.WorkerInfo, error) {
+	return storiface.WorkerInfo{
+		Hostname: s.name,
+		Resources: storiface.WorkerResources{
+			MemPhysical: 128 << 30,
+			MemSwap:     200 << 30,
+			MemReserved: 2 << 30,
+			CPUs:        32,
+			GPUs:        []string{"a GPU"},
+		},
+	}, nil
+}
+
+func (s *schedTestWorker) Closing(ctx context.Context) (<-chan struct{}, error) {
+	return s.closing, nil
+}
+
+func (s *schedTestWorker) Close() error {
+	if !s.closed {
+		log.Info("close schedTestWorker")
+		s.closed = true
+		close(s.closing)
+	}
+	return nil
+}
+
+var _ Worker = &schedTestWorker{}
+
+func addTestWorker(t *testing.T, sched *scheduler, index *stores.Index, name string, taskTypes map[sealtasks.TaskType]struct{}) {
+	w := &schedTestWorker{
+		name:      name,
+		taskTypes: taskTypes,
+		paths:     []stores.StoragePath{{ID: "bb-8", Weight: 2, LocalPath: "<octopus>food</octopus>", CanSeal: true, CanStore: true}},
+
+		closing: make(chan struct{}),
+	}
+
+	for _, path := range w.paths {
+		err := index.StorageAttach(context.TODO(), stores.StorageInfo{
+			ID:       path.ID,
+			URLs:     nil,
+			Weight:   path.Weight,
+			CanSeal:  path.CanSeal,
+			CanStore: path.CanStore,
+		}, fsutil.FsStat{
+			Capacity:  1 << 40,
+			Available: 1 << 40,
+			Reserved:  3,
+		})
+		require.NoError(t, err)
+	}
+
+	info, err := w.Info(context.TODO())
+	require.NoError(t, err)
+
+	sched.newWorkers <- &workerHandle{
+		w: w,
+		wt: &workTracker{
+			running: map[uint64]storiface.WorkerJob{},
+		},
+		info:      info,
+		preparing: &activeResources{},
+		active:    &activeResources{},
+	}
+}
+
+func TestSchedStartStop(t *testing.T) {
+	spt := abi.RegisteredSealProof_StackedDrg32GiBV1
+	sched := newScheduler(spt)
+	go sched.runSched()
+
+	addTestWorker(t, sched, stores.NewIndex(), "fred", nil)
+
+	require.NoError(t, sched.Close(context.TODO()))
+}
+
+func TestSched(t *testing.T) {
+	ctx, done := context.WithTimeout(context.Background(), 30*time.Second)
+	defer done()
+
+	spt := abi.RegisteredSealProof_StackedDrg32GiBV1
+
+	type workerSpec struct {
+		name      string
+		taskTypes map[sealtasks.TaskType]struct{}
+	}
+
+	noopAction := func(ctx context.Context, w Worker) error {
+		return nil
+	}
+
+	type runMeta struct {
+		done map[string]chan struct{}
+
+		wg sync.WaitGroup
+	}
+
+	type task func(*testing.T, *scheduler, *stores.Index, *runMeta)
+
+	sched := func(taskName, expectWorker string, sid abi.SectorNumber, taskType sealtasks.TaskType) task {
+		_, _, l, _ := runtime.Caller(1)
+		_, _, l2, _ := runtime.Caller(2)
+
+		return func(t *testing.T, sched *scheduler, index *stores.Index, rm *runMeta) {
+			done := make(chan struct{})
+			rm.done[taskName] = done
+
+			sel := newAllocSelector(index, stores.FTCache, stores.PathSealing)
+
+			rm.wg.Add(1)
+			go func() {
+				defer rm.wg.Done()
+
+				sectorNum := abi.SectorID{
+					Miner:  8,
+					Number: sid,
+				}
+
+				err := sched.Schedule(ctx, sectorNum, taskType, sel, func(ctx context.Context, w Worker) error {
+					wi, err := w.Info(ctx)
+					require.NoError(t, err)
+
+					require.Equal(t, expectWorker, wi.Hostname)
+
+					log.Info("IN  ", taskName)
+
+					for {
+						_, ok := <-done
+						if !ok {
+							break
+						}
+					}
+
+					log.Info("OUT ", taskName)
+
+					return nil
+				}, noopAction)
+				require.NoError(t, err, fmt.Sprint(l, l2))
+			}()
+
+			<-sched.testSync
+		}
+	}
+
+	taskStarted := func(name string) task {
+		_, _, l, _ := runtime.Caller(1)
+		_, _, l2, _ := runtime.Caller(2)
+		return func(t *testing.T, sched *scheduler, index *stores.Index, rm *runMeta) {
+			select {
+			case rm.done[name] <- struct{}{}:
+			case <-ctx.Done():
+				t.Fatal("ctx error", ctx.Err(), l, l2)
+			}
+		}
+	}
+
+	taskDone := func(name string) task {
+		_, _, l, _ := runtime.Caller(1)
+		_, _, l2, _ := runtime.Caller(2)
+		return func(t *testing.T, sched *scheduler, index *stores.Index, rm *runMeta) {
+			select {
+			case rm.done[name] <- struct{}{}:
+			case <-ctx.Done():
+				t.Fatal("ctx error", ctx.Err(), l, l2)
+			}
+			close(rm.done[name])
+		}
+	}
+
+	taskNotScheduled := func(name string) task {
+		_, _, l, _ := runtime.Caller(1)
+		_, _, l2, _ := runtime.Caller(2)
+		return func(t *testing.T, sched *scheduler, index *stores.Index, rm *runMeta) {
+			select {
+			case rm.done[name] <- struct{}{}:
+				t.Fatal("not expected", l, l2)
+			case <-time.After(10 * time.Millisecond): // TODO: better synchronization thingy
+			}
+		}
+	}
+
+	testFunc := func(workers []workerSpec, tasks []task) func(t *testing.T) {
+		return func(t *testing.T) {
+			index := stores.NewIndex()
+
+			sched := newScheduler(spt)
+			sched.testSync = make(chan struct{})
+
+			go sched.runSched()
+
+			for _, worker := range workers {
+				addTestWorker(t, sched, index, worker.name, worker.taskTypes)
+			}
+
+			rm := runMeta{
+				done: map[string]chan struct{}{},
+			}
+
+			for _, task := range tasks {
+				task(t, sched, index, &rm)
+			}
+
+			log.Info("wait for async stuff")
+			rm.wg.Wait()
+
+			require.NoError(t, sched.Close(context.TODO()))
+		}
+	}
+
+	multTask := func(tasks ...task) task {
+		return func(t *testing.T, s *scheduler, index *stores.Index, meta *runMeta) {
+			for _, tsk := range tasks {
+				tsk(t, s, index, meta)
+			}
+		}
+	}
+
+	t.Run("one-pc1", testFunc([]workerSpec{
+		{name: "fred", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit1: {}}},
+	}, []task{
+		sched("pc1-1", "fred", 8, sealtasks.TTPreCommit1),
+		taskDone("pc1-1"),
+	}))
+
+	t.Run("pc1-2workers-1", testFunc([]workerSpec{
+		{name: "fred2", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit2: {}}},
+		{name: "fred1", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit1: {}}},
+	}, []task{
+		sched("pc1-1", "fred1", 8, sealtasks.TTPreCommit1),
+		taskDone("pc1-1"),
+	}))
+
+	t.Run("pc1-2workers-2", testFunc([]workerSpec{
+		{name: "fred1", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit1: {}}},
+		{name: "fred2", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit2: {}}},
+	}, []task{
+		sched("pc1-1", "fred1", 8, sealtasks.TTPreCommit1),
+		taskDone("pc1-1"),
+	}))
+
+	t.Run("pc1-block-pc2", testFunc([]workerSpec{
+		{name: "fred", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit1: {}, sealtasks.TTPreCommit2: {}}},
+	}, []task{
+		sched("pc1", "fred", 8, sealtasks.TTPreCommit1),
+		taskStarted("pc1"),
+
+		sched("pc2", "fred", 8, sealtasks.TTPreCommit2),
+		taskNotScheduled("pc2"),
+
+		taskDone("pc1"),
+		taskDone("pc2"),
+	}))
+
+	t.Run("pc2-block-pc1", testFunc([]workerSpec{
+		{name: "fred", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit1: {}, sealtasks.TTPreCommit2: {}}},
+	}, []task{
+		sched("pc2", "fred", 8, sealtasks.TTPreCommit2),
+		taskStarted("pc2"),
+
+		sched("pc1", "fred", 8, sealtasks.TTPreCommit1),
+		taskNotScheduled("pc1"),
+
+		taskDone("pc2"),
+		taskDone("pc1"),
+	}))
+
+	t.Run("pc1-batching", testFunc([]workerSpec{
+		{name: "fred", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit1: {}}},
+	}, []task{
+		sched("t1", "fred", 8, sealtasks.TTPreCommit1),
+		taskStarted("t1"),
+
+		sched("t2", "fred", 8, sealtasks.TTPreCommit1),
+		taskStarted("t2"),
+
+		// with worker settings, we can only run 2 parallel PC1s
+
+		// start 2 more to fill fetch buffer
+
+		sched("t3", "fred", 8, sealtasks.TTPreCommit1),
+		taskNotScheduled("t3"),
+
+		sched("t4", "fred", 8, sealtasks.TTPreCommit1),
+		taskNotScheduled("t4"),
+
+		taskDone("t1"),
+		taskDone("t2"),
+
+		taskStarted("t3"),
+		taskStarted("t4"),
+
+		taskDone("t3"),
+		taskDone("t4"),
+	}))
+
+	twoPC1 := func(prefix string, sid abi.SectorNumber, schedAssert func(name string) task) task {
+		return multTask(
+			sched(prefix+"-a", "fred", sid, sealtasks.TTPreCommit1),
+			schedAssert(prefix+"-a"),
+
+			sched(prefix+"-b", "fred", sid+1, sealtasks.TTPreCommit1),
+			schedAssert(prefix+"-b"),
+		)
+	}
+
+	twoPC1Act := func(prefix string, schedAssert func(name string) task) task {
+		return multTask(
+			schedAssert(prefix+"-a"),
+			schedAssert(prefix+"-b"),
+		)
+	}
+
+	// run this one a bunch of times, it had a very annoying tendency to fail randomly
+	for i := 0; i < 40; i++ {
+		t.Run("pc1-pc2-prio", testFunc([]workerSpec{
+			{name: "fred", taskTypes: map[sealtasks.TaskType]struct{}{sealtasks.TTPreCommit1: {}, sealtasks.TTPreCommit2: {}}},
+		}, []task{
+			// fill queues
+			twoPC1("w0", 0, taskStarted),
+			twoPC1("w1", 2, taskNotScheduled),
+
+			// windowed
+
+			sched("t1", "fred", 8, sealtasks.TTPreCommit1),
+			taskNotScheduled("t1"),
+
+			sched("t2", "fred", 9, sealtasks.TTPreCommit1),
+			taskNotScheduled("t2"),
+
+			sched("t3", "fred", 10, sealtasks.TTPreCommit2),
+			taskNotScheduled("t3"),
+
+			twoPC1Act("w0", taskDone),
+			twoPC1Act("w1", taskStarted),
+
+			twoPC1Act("w1", taskDone),
+
+			taskStarted("t3"),
+			taskNotScheduled("t1"),
+			taskNotScheduled("t2"),
+
+			taskDone("t3"),
+
+			taskStarted("t1"),
+			taskStarted("t2"),
+
+			taskDone("t1"),
+			taskDone("t2"),
+		}))
+	}
+}
diff --git a/sched_watch.go b/sched_watch.go
index 214489083..d93cf1af3 100644
--- a/sched_watch.go
+++ b/sched_watch.go
@@ -74,7 +74,11 @@ func (sh *scheduler) runWorkerWatcher() {
 
 			caseToWorker[toSet] = wid
 		default:
-			wid := caseToWorker[n]
+			wid, found := caseToWorker[n]
+			if !found {
+				log.Errorf("worker ID not found for case %d", n)
+				continue
+			}
 
 			delete(caseToWorker, n)
 			cases[n] = reflect.SelectCase{
diff --git a/sealtasks/task.go b/sealtasks/task.go
index 978107c85..ad5ce01bb 100644
--- a/sealtasks/task.go
+++ b/sealtasks/task.go
@@ -28,6 +28,30 @@ var order = map[TaskType]int{
 	TTReadUnsealed: 0,
 }
 
+var shortNames = map[TaskType]string{
+	TTAddPiece: "AP ",
+
+	TTPreCommit1: "PC1",
+	TTPreCommit2: "PC2",
+	TTCommit1:    "C1 ",
+	TTCommit2:    "C2 ",
+
+	TTFinalize: "FIN",
+
+	TTFetch:        "GET",
+	TTUnseal:       "UNS",
+	TTReadUnsealed: "RD ",
+}
+
 func (a TaskType) Less(b TaskType) bool {
 	return order[a] < order[b]
 }
+
+func (a TaskType) Short() string {
+	n, ok := shortNames[a]
+	if !ok {
+		return "UNK"
+	}
+
+	return n
+}
diff --git a/selector_alloc.go b/selector_alloc.go
index 874bf7bb0..cf7937587 100644
--- a/selector_alloc.go
+++ b/selector_alloc.go
@@ -17,12 +17,12 @@ type allocSelector struct {
 	ptype stores.PathType
 }
 
-func newAllocSelector(ctx context.Context, index stores.SectorIndex, alloc stores.SectorFileType, ptype stores.PathType) (*allocSelector, error) {
+func newAllocSelector(index stores.SectorIndex, alloc stores.SectorFileType, ptype stores.PathType) *allocSelector {
 	return &allocSelector{
 		index: index,
 		alloc: alloc,
 		ptype: ptype,
-	}, nil
+	}
 }
 
 func (s *allocSelector) Ok(ctx context.Context, task sealtasks.TaskType, spt abi.RegisteredSealProof, whnd *workerHandle) (bool, error) {
diff --git a/selector_existing.go b/selector_existing.go
index 3f99010cb..a11c39007 100644
--- a/selector_existing.go
+++ b/selector_existing.go
@@ -12,18 +12,19 @@ import (
 )
 
 type existingSelector struct {
-	best []stores.SectorStorageInfo
+	index      stores.SectorIndex
+	sector     abi.SectorID
+	alloc      stores.SectorFileType
+	allowFetch bool
 }
 
-func newExistingSelector(ctx context.Context, index stores.SectorIndex, sector abi.SectorID, alloc stores.SectorFileType, allowFetch bool) (*existingSelector, error) {
-	best, err := index.StorageFindSector(ctx, sector, alloc, allowFetch)
-	if err != nil {
-		return nil, err
-	}
-
+func newExistingSelector(index stores.SectorIndex, sector abi.SectorID, alloc stores.SectorFileType, allowFetch bool) *existingSelector {
 	return &existingSelector{
-		best: best,
-	}, nil
+		index:      index,
+		sector:     sector,
+		alloc:      alloc,
+		allowFetch: allowFetch,
+	}
 }
 
 func (s *existingSelector) Ok(ctx context.Context, task sealtasks.TaskType, spt abi.RegisteredSealProof, whnd *workerHandle) (bool, error) {
@@ -45,7 +46,12 @@ func (s *existingSelector) Ok(ctx context.Context, task sealtasks.TaskType, spt
 		have[path.ID] = struct{}{}
 	}
 
-	for _, info := range s.best {
+	best, err := s.index.StorageFindSector(ctx, s.sector, s.alloc, s.allowFetch)
+	if err != nil {
+		return false, xerrors.Errorf("finding best storage: %w", err)
+	}
+
+	for _, info := range best {
 		if _, ok := have[info.ID]; ok {
 			return true, nil
 		}
diff --git a/stats.go b/stats.go
index dbbee07f3..ee88898a4 100644
--- a/stats.go
+++ b/stats.go
@@ -20,3 +20,16 @@ func (m *Manager) WorkerStats() map[uint64]storiface.WorkerStats {
 
 	return out
 }
+
+func (m *Manager) WorkerJobs() map[uint64][]storiface.WorkerJob {
+	m.sched.workersLk.Lock()
+	defer m.sched.workersLk.Unlock()
+
+	out := map[uint64][]storiface.WorkerJob{}
+
+	for id, handle := range m.sched.workers {
+		out[uint64(id)] = handle.wt.Running()
+	}
+
+	return out
+}
diff --git a/stores/filetype.go b/stores/filetype.go
index c31dfefb2..650b92f71 100644
--- a/stores/filetype.go
+++ b/stores/filetype.go
@@ -19,15 +19,17 @@ const (
 	FTNone SectorFileType = 0
 )
 
+const FSOverheadDen = 10
+
 var FSOverheadSeal = map[SectorFileType]int{ // 10x overheads
-	FTUnsealed: 10,
-	FTSealed:   10,
-	FTCache:    70, // TODO: confirm for 32G
+	FTUnsealed: FSOverheadDen,
+	FTSealed:   FSOverheadDen,
+	FTCache:    141, // 11 layers + D(2x ssize) + C + R
 }
 
 var FsOverheadFinalized = map[SectorFileType]int{
-	FTUnsealed: 10,
-	FTSealed:   10,
+	FTUnsealed: FSOverheadDen,
+	FTSealed:   FSOverheadDen,
 	FTCache:    2,
 }
 
@@ -67,7 +69,7 @@ func (t SectorFileType) SealSpaceUse(spt abi.RegisteredSealProof) (uint64, error
 			return 0, xerrors.Errorf("no seal overhead info for %s", pathType)
 		}
 
-		need += uint64(oh) * uint64(ssize) / 10
+		need += uint64(oh) * uint64(ssize) / FSOverheadDen
 	}
 
 	return need, nil
diff --git a/stores/http_handler.go b/stores/http_handler.go
index 60f8a41c5..4f0556138 100644
--- a/stores/http_handler.go
+++ b/stores/http_handler.go
@@ -72,13 +72,15 @@ func (handler *FetchHandler) remoteGetSector(w http.ResponseWriter, r *http.Requ
 	// The caller has a lock on this sector already, no need to get one here
 
 	// passing 0 spt because we don't allocate anything
-	paths, _, err := handler.Local.AcquireSector(r.Context(), id, 0, ft, FTNone, false, AcquireMove)
+	paths, _, err := handler.Local.AcquireSector(r.Context(), id, 0, ft, FTNone, PathStorage, AcquireMove)
 	if err != nil {
 		log.Error("%+v", err)
 		w.WriteHeader(500)
 		return
 	}
 
+	// TODO: reserve local storage here
+
 	path := PathByType(paths, ft)
 	if path == "" {
 		log.Error("acquired path was empty")
diff --git a/stores/index.go b/stores/index.go
index 049e2dc20..acad2abaa 100644
--- a/stores/index.go
+++ b/stores/index.go
@@ -2,6 +2,7 @@ package stores
 
 import (
 	"context"
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"net/url"
 	gopath "path"
 	"sort"
@@ -28,13 +29,10 @@ type StorageInfo struct {
 
 	CanSeal  bool
 	CanStore bool
-
-	LastHeartbeat time.Time
-	HeartbeatErr  error
 }
 
 type HealthReport struct {
-	Stat FsStat
+	Stat fsutil.FsStat
 	Err  error
 }
 
@@ -50,7 +48,7 @@ type SectorStorageInfo struct {
 }
 
 type SectorIndex interface { // part of storage-miner api
-	StorageAttach(context.Context, StorageInfo, FsStat) error
+	StorageAttach(context.Context, StorageInfo, fsutil.FsStat) error
 	StorageInfo(context.Context, ID) (StorageInfo, error)
 	StorageReportHealth(context.Context, ID, HealthReport) error
 
@@ -77,7 +75,7 @@ type declMeta struct {
 
 type storageEntry struct {
 	info *StorageInfo
-	fsi  FsStat
+	fsi  fsutil.FsStat
 
 	lastHeartbeat time.Time
 	heartbeatErr  error
@@ -130,7 +128,7 @@ func (i *Index) StorageList(ctx context.Context) (map[ID][]Decl, error) {
 	return out, nil
 }
 
-func (i *Index) StorageAttach(ctx context.Context, si StorageInfo, st FsStat) error {
+func (i *Index) StorageAttach(ctx context.Context, si StorageInfo, st fsutil.FsStat) error {
 	i.lk.Lock()
 	defer i.lk.Unlock()
 
@@ -361,7 +359,7 @@ func (i *Index) StorageBestAlloc(ctx context.Context, allocate SectorFileType, s
 			continue
 		}
 
-		if spaceReq > p.fsi.Available {
+		if spaceReq > uint64(p.fsi.Available) {
 			log.Debugf("not allocating on %s, out of space (available: %d, need: %d)", p.info.ID, p.fsi.Available, spaceReq)
 			continue
 		}
diff --git a/stores/interface.go b/stores/interface.go
index 54aaec90c..142769b1b 100644
--- a/stores/interface.go
+++ b/stores/interface.go
@@ -2,25 +2,22 @@ package stores
 
 import (
 	"context"
-	"syscall"
-
-	"golang.org/x/xerrors"
-
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"github.com/filecoin-project/specs-actors/actors/abi"
 )
 
-type PathType bool
+type PathType string
 
 const (
-	PathStorage = false
-	PathSealing = true
+	PathStorage PathType = "storage"
+	PathSealing PathType = "sealing"
 )
 
 type AcquireMode string
 
 const (
-	AcquireMove = "move"
-	AcquireCopy = "copy"
+	AcquireMove AcquireMode = "move"
+	AcquireCopy AcquireMode = "copy"
 )
 
 type Store interface {
@@ -34,23 +31,5 @@ type Store interface {
 	// move sectors into storage
 	MoveStorage(ctx context.Context, s abi.SectorID, spt abi.RegisteredSealProof, types SectorFileType) error
 
-	FsStat(ctx context.Context, id ID) (FsStat, error)
-}
-
-func Stat(path string) (FsStat, error) {
-	var stat syscall.Statfs_t
-	if err := syscall.Statfs(path, &stat); err != nil {
-		return FsStat{}, xerrors.Errorf("statfs: %w", err)
-	}
-
-	return FsStat{
-		Capacity:  stat.Blocks * uint64(stat.Bsize),
-		Available: stat.Bavail * uint64(stat.Bsize),
-	}, nil
-}
-
-type FsStat struct {
-	Capacity  uint64
-	Available uint64 // Available to use for sector storage
-	Used      uint64
+	FsStat(ctx context.Context, id ID) (fsutil.FsStat, error)
 }
diff --git a/stores/local.go b/stores/local.go
index 26b7ccb75..9efab6480 100644
--- a/stores/local.go
+++ b/stores/local.go
@@ -13,6 +13,7 @@ import (
 
 	"golang.org/x/xerrors"
 
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"github.com/filecoin-project/specs-actors/actors/abi"
 )
 
@@ -48,7 +49,11 @@ type LocalStorage interface {
 	GetStorage() (StorageConfig, error)
 	SetStorage(func(*StorageConfig)) error
 
-	Stat(path string) (FsStat, error)
+	Stat(path string) (fsutil.FsStat, error)
+
+	// returns real disk usage for a file/directory
+	// os.ErrNotExit when file doesn't exist
+	DiskUsage(path string) (int64, error)
 }
 
 const MetaFile = "sectorstore.json"
@@ -67,6 +72,60 @@ type Local struct {
 
 type path struct {
 	local string // absolute local path
+
+	reserved     int64
+	reservations map[abi.SectorID]SectorFileType
+}
+
+func (p *path) stat(ls LocalStorage) (fsutil.FsStat, error) {
+	stat, err := ls.Stat(p.local)
+	if err != nil {
+		return fsutil.FsStat{}, xerrors.Errorf("stat %s: %w", p.local, err)
+	}
+
+	stat.Reserved = p.reserved
+
+	for id, ft := range p.reservations {
+		for _, fileType := range PathTypes {
+			if fileType&ft == 0 {
+				continue
+			}
+
+			sp := p.sectorPath(id, fileType)
+
+			used, err := ls.DiskUsage(sp)
+			if err == os.ErrNotExist {
+				p, ferr := tempFetchDest(sp, false)
+				if ferr != nil {
+					return fsutil.FsStat{}, ferr
+				}
+
+				used, err = ls.DiskUsage(p)
+			}
+			if err != nil {
+				log.Errorf("getting disk usage of '%s': %+v", p.sectorPath(id, fileType), err)
+				continue
+			}
+
+			stat.Reserved -= used
+		}
+	}
+
+	if stat.Reserved < 0 {
+		log.Warnf("negative reserved storage: p.reserved=%d, reserved: %d", p.reserved, stat.Reserved)
+		stat.Reserved = 0
+	}
+
+	stat.Available -= stat.Reserved
+	if stat.Available < 0 {
+		stat.Available = 0
+	}
+
+	return stat, err
+}
+
+func (p *path) sectorPath(sid abi.SectorID, fileType SectorFileType) string {
+	return filepath.Join(p.local, fileType.String(), SectorName(sid))
 }
 
 func NewLocal(ctx context.Context, ls LocalStorage, index SectorIndex, urls []string) (*Local, error) {
@@ -98,9 +157,12 @@ func (st *Local) OpenPath(ctx context.Context, p string) error {
 
 	out := &path{
 		local: p,
+
+		reserved:     0,
+		reservations: map[abi.SectorID]SectorFileType{},
 	}
 
-	fst, err := st.localStorage.Stat(p)
+	fst, err := out.stat(st.localStorage)
 	if err != nil {
 		return err
 	}
@@ -130,6 +192,10 @@ func (st *Local) OpenPath(ctx context.Context, p string) error {
 		}
 
 		for _, ent := range ents {
+			if ent.Name() == FetchTempSubdir {
+				continue
+			}
+
 			sid, err := ParseSectorID(ent.Name())
 			if err != nil {
 				return xerrors.Errorf("parse sector id %s: %w", ent.Name(), err)
@@ -179,7 +245,7 @@ func (st *Local) reportHealth(ctx context.Context) {
 
 		toReport := map[ID]HealthReport{}
 		for id, p := range st.paths {
-			stat, err := st.localStorage.Stat(p.local)
+			stat, err := p.stat(st.localStorage)
 
 			toReport[id] = HealthReport{
 				Stat: stat,
@@ -197,6 +263,61 @@ func (st *Local) reportHealth(ctx context.Context) {
 	}
 }
 
+func (st *Local) Reserve(ctx context.Context, sid abi.SectorID, spt abi.RegisteredSealProof, ft SectorFileType, storageIDs SectorPaths, overheadTab map[SectorFileType]int) (func(), error) {
+	ssize, err := spt.SectorSize()
+	if err != nil {
+		return nil, xerrors.Errorf("getting sector size: %w", err)
+	}
+
+	st.localLk.Lock()
+
+	done := func() {}
+	deferredDone := func() { done() }
+	defer func() {
+		st.localLk.Unlock()
+		deferredDone()
+	}()
+
+	for _, fileType := range PathTypes {
+		if fileType&ft == 0 {
+			continue
+		}
+
+		id := ID(PathByType(storageIDs, fileType))
+
+		p, ok := st.paths[id]
+		if !ok {
+			return nil, errPathNotFound
+		}
+
+		stat, err := p.stat(st.localStorage)
+		if err != nil {
+			return nil, xerrors.Errorf("getting local storage stat: %w", err)
+		}
+
+		overhead := int64(overheadTab[fileType]) * int64(ssize) / FSOverheadDen
+
+		if stat.Available < overhead {
+			return nil, xerrors.Errorf("can't reserve %d bytes in '%s' (id:%s), only %d available", overhead, p.local, id, stat.Available)
+		}
+
+		p.reserved += overhead
+
+		prevDone := done
+		done = func() {
+			prevDone()
+
+			st.localLk.Lock()
+			defer st.localLk.Unlock()
+
+			p.reserved -= overhead
+		}
+	}
+
+	deferredDone = func() {}
+	return done, nil
+}
+
 func (st *Local) AcquireSector(ctx context.Context, sid abi.SectorID, spt abi.RegisteredSealProof, existing SectorFileType, allocate SectorFileType, pathType PathType, op AcquireMode) (SectorPaths, SectorPaths, error) {
 	if existing|allocate != existing^allocate {
 		return SectorPaths{}, SectorPaths{}, xerrors.New("can't both find and allocate a sector")
@@ -229,7 +350,7 @@ func (st *Local) AcquireSector(ctx context.Context, sid abi.SectorID, spt abi.Re
 				continue
 			}
 
-			spath := filepath.Join(p.local, fileType.String(), SectorName(sid))
+			spath := p.sectorPath(sid, fileType)
 			SetPathByType(&out, fileType, spath)
 			SetPathByType(&storageIDs, fileType, string(info.ID))
 
@@ -271,8 +392,9 @@ func (st *Local) AcquireSector(ctx context.Context, sid abi.SectorID, spt abi.Re
 
 			// TODO: Check free space
 
-			best = filepath.Join(p.local, fileType.String(), SectorName(sid))
+			best = p.sectorPath(sid, fileType)
 			bestID = si.ID
+			break
 		}
 
 		if best == "" {
@@ -387,7 +509,7 @@ func (st *Local) removeSector(ctx context.Context, sid abi.SectorID, typ SectorF
 		return xerrors.Errorf("dropping sector from index: %w", err)
 	}
 
-	spath := filepath.Join(p.local, typ.String(), SectorName(sid))
+	spath := p.sectorPath(sid, typ)
 	log.Infof("remove %s", spath)
 
 	if err := os.RemoveAll(spath); err != nil {
@@ -398,12 +520,12 @@ func (st *Local) removeSector(ctx context.Context, sid abi.SectorID, typ SectorF
 }
 
 func (st *Local) MoveStorage(ctx context.Context, s abi.SectorID, spt abi.RegisteredSealProof, types SectorFileType) error {
-	dest, destIds, err := st.AcquireSector(ctx, s, spt, FTNone, types, false, AcquireMove)
+	dest, destIds, err := st.AcquireSector(ctx, s, spt, FTNone, types, PathStorage, AcquireMove)
 	if err != nil {
 		return xerrors.Errorf("acquire dest storage: %w", err)
 	}
 
-	src, srcIds, err := st.AcquireSector(ctx, s, spt, types, FTNone, false, AcquireMove)
+	src, srcIds, err := st.AcquireSector(ctx, s, spt, types, FTNone, PathStorage, AcquireMove)
 	if err != nil {
 		return xerrors.Errorf("acquire src storage: %w", err)
 	}
@@ -454,16 +576,16 @@ func (st *Local) MoveStorage(ctx context.Context, s abi.SectorID, spt abi.Regist
 
 var errPathNotFound = xerrors.Errorf("fsstat: path not found")
 
-func (st *Local) FsStat(ctx context.Context, id ID) (FsStat, error) {
+func (st *Local) FsStat(ctx context.Context, id ID) (fsutil.FsStat, error) {
 	st.localLk.RLock()
 	defer st.localLk.RUnlock()
 
 	p, ok := st.paths[id]
 	if !ok {
-		return FsStat{}, errPathNotFound
+		return fsutil.FsStat{}, errPathNotFound
 	}
 
-	return st.localStorage.Stat(p.local)
+	return p.stat(st.localStorage)
 }
 
 var _ Store = &Local{}
diff --git a/stores/local_test.go b/stores/local_test.go
index 8e654d725..56ac7c020 100644
--- a/stores/local_test.go
+++ b/stores/local_test.go
@@ -3,6 +3,7 @@ package stores
 import (
 	"context"
 	"encoding/json"
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"github.com/google/uuid"
 	"io/ioutil"
 	"os"
@@ -19,6 +20,10 @@ type TestingLocalStorage struct {
 	c    StorageConfig
 }
 
+func (t *TestingLocalStorage) DiskUsage(path string) (int64, error) {
+	return 1, nil
+}
+
 func (t *TestingLocalStorage) GetStorage() (StorageConfig, error) {
 	return t.c, nil
 }
@@ -28,11 +33,10 @@ func (t *TestingLocalStorage) SetStorage(f func(*StorageConfig)) error {
 	return nil
 }
 
-func (t *TestingLocalStorage) Stat(path string) (FsStat, error) {
-	return FsStat{
+func (t *TestingLocalStorage) Stat(path string) (fsutil.FsStat, error) {
+	return fsutil.FsStat{
 		Capacity:  pathSize,
 		Available: pathSize,
-		Used:      0,
 	}, nil
 }
 
diff --git a/stores/remote.go b/stores/remote.go
index 30fe3abf9..93dc2ca58 100644
--- a/stores/remote.go
+++ b/stores/remote.go
@@ -3,6 +3,7 @@ package stores
 import (
 	"context"
 	"encoding/json"
+	"github.com/filecoin-project/sector-storage/fsutil"
 	"io/ioutil"
 	"math/bits"
 	"mime"
@@ -10,6 +11,7 @@ import (
 	"net/url"
 	"os"
 	gopath "path"
+	"path/filepath"
 	"sort"
 	"sync"
 
@@ -23,11 +25,15 @@ import (
 	"github.com/filecoin-project/sector-storage/tarutil"
 )
 
+var FetchTempSubdir = "fetching"
+
 type Remote struct {
 	local *Local
 	index SectorIndex
 	auth  http.Header
 
+	limit chan struct{}
+
 	fetchLk  sync.Mutex
 	fetching map[abi.SectorID]chan struct{}
 }
@@ -40,12 +46,14 @@ func (r *Remote) RemoveCopies(ctx context.Context, s abi.SectorID, types SectorF
 	return r.local.RemoveCopies(ctx, s, types)
 }
 
-func NewRemote(local *Local, index SectorIndex, auth http.Header) *Remote {
+func NewRemote(local *Local, index SectorIndex, auth http.Header, fetchLimit int) *Remote {
 	return &Remote{
 		local: local,
 		index: index,
 		auth:  auth,
 
+		limit: make(chan struct{}, fetchLimit),
+
 		fetching: map[abi.SectorID]chan struct{}{},
 	}
 }
@@ -87,6 +95,33 @@ func (r *Remote) AcquireSector(ctx context.Context, s abi.SectorID, spt abi.Regi
 		return SectorPaths{}, SectorPaths{}, xerrors.Errorf("local acquire error: %w", err)
 	}
 
+	var toFetch SectorFileType
+	for _, fileType := range PathTypes {
+		if fileType&existing == 0 {
+			continue
+		}
+
+		if PathByType(paths, fileType) == "" {
+			toFetch |= fileType
+		}
+	}
+
+	apaths, ids, err := r.local.AcquireSector(ctx, s, spt, FTNone, toFetch, pathType, op)
+	if err != nil {
+		return SectorPaths{}, SectorPaths{}, xerrors.Errorf("allocate local sector for fetching: %w", err)
+	}
+
+	odt := FSOverheadSeal
+	if pathType == PathStorage {
+		odt = FsOverheadFinalized
+	}
+
+	releaseStorage, err := r.local.Reserve(ctx, s, spt, toFetch, ids, odt)
+	if err != nil {
+		return SectorPaths{}, SectorPaths{}, xerrors.Errorf("reserving storage space: %w", err)
+	}
+	defer releaseStorage()
+
 	for _, fileType := range PathTypes {
 		if fileType&existing == 0 {
 			continue
@@ -96,15 +131,18 @@ func (r *Remote) AcquireSector(ctx context.Context, s abi.SectorID, spt abi.Regi
 			continue
 		}
 
-		ap, storageID, url, err := r.acquireFromRemote(ctx, s, spt, fileType, pathType, op)
+		dest := PathByType(apaths, fileType)
+		storageID := PathByType(ids, fileType)
+
+		url, err := r.acquireFromRemote(ctx, s, fileType, dest)
 		if err != nil {
 			return SectorPaths{}, SectorPaths{}, err
 		}
 
-		SetPathByType(&paths, fileType, ap)
-		SetPathByType(&stores, fileType, string(storageID))
+		SetPathByType(&paths, fileType, dest)
+		SetPathByType(&stores, fileType, storageID)
 
-		if err := r.index.StorageDeclareSector(ctx, storageID, s, fileType, op == AcquireMove); err != nil {
+		if err := r.index.StorageDeclareSector(ctx, ID(storageID), s, fileType, op == AcquireMove); err != nil {
 			log.Warnf("declaring sector %v in %s failed: %+v", s, storageID, err)
 			continue
 		}
@@ -119,51 +157,84 @@ func (r *Remote) AcquireSector(ctx context.Context, s abi.SectorID, spt abi.Regi
 	return paths, stores, nil
 }
 
-func (r *Remote) acquireFromRemote(ctx context.Context, s abi.SectorID, spt abi.RegisteredSealProof, fileType SectorFileType, pathType PathType, op AcquireMode) (string, ID, string, error) {
+func tempFetchDest(spath string, create bool) (string, error) {
+	st, b := filepath.Split(spath)
+	tempdir := filepath.Join(st, FetchTempSubdir)
+	if create {
+		if err := os.MkdirAll(tempdir, 0755); err != nil {
+			return "", xerrors.Errorf("creating temp fetch dir: %w", err)
+		}
+	}
+
+	return filepath.Join(tempdir, b), nil
+}
+
+func (r *Remote) acquireFromRemote(ctx context.Context, s abi.SectorID, fileType SectorFileType, dest string) (string, error) {
 	si, err := r.index.StorageFindSector(ctx, s, fileType, false)
 	if err != nil {
-		return "", "", "", err
+		return "", err
 	}
 
 	if len(si) == 0 {
-		return "", "", "", xerrors.Errorf("failed to acquire sector %v from remote(%d): %w", s, fileType, storiface.ErrSectorNotFound)
+		return "", xerrors.Errorf("failed to acquire sector %v from remote(%d): %w", s, fileType, storiface.ErrSectorNotFound)
 	}
 
 	sort.Slice(si, func(i, j int) bool {
 		return si[i].Weight < si[j].Weight
 	})
 
-	apaths, ids, err := r.local.AcquireSector(ctx, s, spt, FTNone, fileType, pathType, op)
-	if err != nil {
-		return "", "", "", xerrors.Errorf("allocate local sector for fetching: %w", err)
-	}
-	dest := PathByType(apaths, fileType)
-	storageID := PathByType(ids, fileType)
-
 	var merr error
 	for _, info := range si {
 		// TODO: see what we have local, prefer that
 
 		for _, url := range info.URLs {
-			err := r.fetch(ctx, url, dest)
+			tempDest, err := tempFetchDest(dest, true)
 			if err != nil {
-				merr = multierror.Append(merr, xerrors.Errorf("fetch error %s (storage %s) -> %s: %w", url, info.ID, dest, err))
+				return "", err
+			}
+
+			if err := os.RemoveAll(dest); err != nil {
+				return "", xerrors.Errorf("removing dest: %w", err)
+			}
+
+			err = r.fetch(ctx, url, tempDest)
+			if err != nil {
+				merr = multierror.Append(merr, xerrors.Errorf("fetch error %s (storage %s) -> %s: %w", url, info.ID, tempDest, err))
 				continue
 			}
 
+			if err := move(tempDest, dest); err != nil {
+				return "", xerrors.Errorf("fetch move error (storage %s) %s -> %s: %w", info.ID, tempDest, dest, err)
+			}
+
 			if merr != nil {
 				log.Warnw("acquireFromRemote encountered errors when fetching sector from remote", "errors", merr)
 			}
-			return dest, ID(storageID), url, nil
+			return url, nil
 		}
 	}
 
-	return "", "", "", xerrors.Errorf("failed to acquire sector %v from remote (tried %v): %w", s, si, merr)
+	return "", xerrors.Errorf("failed to acquire sector %v from remote (tried %v): %w", s, si, merr)
 }
 
 func (r *Remote) fetch(ctx context.Context, url, outname string) error {
 	log.Infof("Fetch %s -> %s", url, outname)
 
+	if len(r.limit) >= cap(r.limit) {
+		log.Infof("Throttling fetch, %d already running", len(r.limit))
+	}
+
+	// TODO: Smarter throttling
+	//  * Priority (just going sequentially is still pretty good)
+	//  * Per interface
+	//  * Aware of remote load
+	select {
+	case r.limit <- struct{}{}:
+		defer func() { <-r.limit }()
+	case <-ctx.Done():
+		return xerrors.Errorf("context error while waiting for fetch limiter: %w", ctx.Err())
+	}
+
 	req, err := http.NewRequest("GET", url, nil)
 	if err != nil {
 		return xerrors.Errorf("request: %w", err)
@@ -270,7 +341,7 @@ func (r *Remote) deleteFromRemote(ctx context.Context, url string) error {
 	return nil
 }
 
-func (r *Remote) FsStat(ctx context.Context, id ID) (FsStat, error) {
+func (r *Remote) FsStat(ctx context.Context, id ID) (fsutil.FsStat, error) {
 	st, err := r.local.FsStat(ctx, id)
 	switch err {
 	case nil:
@@ -278,53 +349,53 @@ func (r *Remote) FsStat(ctx context.Context, id ID) (FsStat, error) {
 	case errPathNotFound:
 		break
 	default:
-		return FsStat{}, xerrors.Errorf("local stat: %w", err)
+		return fsutil.FsStat{}, xerrors.Errorf("local stat: %w", err)
 	}
 
 	si, err := r.index.StorageInfo(ctx, id)
 	if err != nil {
-		return FsStat{}, xerrors.Errorf("getting remote storage info: %w", err)
+		return fsutil.FsStat{}, xerrors.Errorf("getting remote storage info: %w", err)
 	}
 
 	if len(si.URLs) == 0 {
-		return FsStat{}, xerrors.Errorf("no known URLs for remote storage %s", id)
+		return fsutil.FsStat{}, xerrors.Errorf("no known URLs for remote storage %s", id)
 	}
 
 	rl, err := url.Parse(si.URLs[0])
 	if err != nil {
-		return FsStat{}, xerrors.Errorf("failed to parse url: %w", err)
+		return fsutil.FsStat{}, xerrors.Errorf("failed to parse url: %w", err)
 	}
 
 	rl.Path = gopath.Join(rl.Path, "stat", string(id))
 
 	req, err := http.NewRequest("GET", rl.String(), nil)
 	if err != nil {
-		return FsStat{}, xerrors.Errorf("request: %w", err)
+		return fsutil.FsStat{}, xerrors.Errorf("request: %w", err)
 	}
 	req.Header = r.auth
 	req = req.WithContext(ctx)
 
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
-		return FsStat{}, xerrors.Errorf("do request: %w", err)
+		return fsutil.FsStat{}, xerrors.Errorf("do request: %w", err)
 	}
 	switch resp.StatusCode {
 	case 200:
 		break
 	case 404:
-		return FsStat{}, errPathNotFound
+		return fsutil.FsStat{}, errPathNotFound
 	case 500:
 		b, err := ioutil.ReadAll(resp.Body)
 		if err != nil {
-			return FsStat{}, xerrors.Errorf("fsstat: got http 500, then failed to read the error: %w", err)
+			return fsutil.FsStat{}, xerrors.Errorf("fsstat: got http 500, then failed to read the error: %w", err)
 		}
 
-		return FsStat{}, xerrors.Errorf("fsstat: got http 500: %s", string(b))
+		return fsutil.FsStat{}, xerrors.Errorf("fsstat: got http 500: %s", string(b))
 	}
 
-	var out FsStat
+	var out fsutil.FsStat
 	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
-		return FsStat{}, xerrors.Errorf("decoding fsstat: %w", err)
+		return fsutil.FsStat{}, xerrors.Errorf("decoding fsstat: %w", err)
 	}
 
 	defer resp.Body.Close()
diff --git a/storiface/worker.go b/storiface/worker.go
index 0f49e8971..01ef59d36 100644
--- a/storiface/worker.go
+++ b/storiface/worker.go
@@ -1,5 +1,12 @@
 package storiface
 
+import (
+	"time"
+
+	"github.com/filecoin-project/sector-storage/sealtasks"
+	"github.com/filecoin-project/specs-actors/actors/abi"
+)
+
 type WorkerInfo struct {
 	Hostname string
 
@@ -24,3 +31,11 @@ type WorkerStats struct {
 	GpuUsed    bool
 	CpuUse     uint64
 }
+
+type WorkerJob struct {
+	ID     uint64
+	Sector abi.SectorID
+	Task   sealtasks.TaskType
+
+	Start time.Time
+}
diff --git a/testworker_test.go b/testworker_test.go
index 5ca51b771..40151a84d 100644
--- a/testworker_test.go
+++ b/testworker_test.go
@@ -37,7 +37,7 @@ func newTestWorker(wcfg WorkerConfig, lstor *stores.Local) *testWorker {
 		acceptTasks: acceptTasks,
 		lstor:       lstor,
 
-		mockSeal: mock.NewMockSectorMgr(ssize),
+		mockSeal: mock.NewMockSectorMgr(ssize, nil),
 	}
 }
 
@@ -53,7 +53,7 @@ func (t *testWorker) UnsealPiece(ctx context.Context, id abi.SectorID, index sto
 	panic("implement me")
 }
 
-func (t *testWorker) ReadPiece(ctx context.Context, writer io.Writer, id abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) error {
+func (t *testWorker) ReadPiece(ctx context.Context, writer io.Writer, id abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) (bool, error) {
 	panic("implement me")
 }
 
diff --git a/work_tracker.go b/work_tracker.go
new file mode 100644
index 000000000..7453752c9
--- /dev/null
+++ b/work_tracker.go
@@ -0,0 +1,129 @@
+package sectorstorage
+
+import (
+	"context"
+	"io"
+	"sync"
+	"time"
+
+	"github.com/ipfs/go-cid"
+
+	"github.com/filecoin-project/specs-actors/actors/abi"
+	"github.com/filecoin-project/specs-storage/storage"
+
+	"github.com/filecoin-project/sector-storage/sealtasks"
+	"github.com/filecoin-project/sector-storage/stores"
+	"github.com/filecoin-project/sector-storage/storiface"
+)
+
+type workTracker struct {
+	lk sync.Mutex
+
+	ctr     uint64
+	running map[uint64]storiface.WorkerJob
+
+	// TODO: done, aggregate stats, queue stats, scheduler feedback
+}
+
+func (wt *workTracker) track(sid abi.SectorID, task sealtasks.TaskType) func() {
+	wt.lk.Lock()
+	defer wt.lk.Unlock()
+
+	id := wt.ctr
+	wt.ctr++
+
+	wt.running[id] = storiface.WorkerJob{
+		ID:     id,
+		Sector: sid,
+		Task:   task,
+		Start:  time.Now(),
+	}
+
+	return func() {
+		wt.lk.Lock()
+		defer wt.lk.Unlock()
+
+		delete(wt.running, id)
+	}
+}
+
+func (wt *workTracker) worker(w Worker) Worker {
+	return &trackedWorker{
+		Worker:  w,
+		tracker: wt,
+	}
+}
+
+func (wt *workTracker) Running() []storiface.WorkerJob {
+	wt.lk.Lock()
+	defer wt.lk.Unlock()
+
+	out := make([]storiface.WorkerJob, 0, len(wt.running))
+	for _, job := range wt.running {
+		out = append(out, job)
+	}
+
+	return out
+}
+
+type trackedWorker struct {
+	Worker
+
+	tracker *workTracker
+}
+
+func (t *trackedWorker) SealPreCommit1(ctx context.Context, sector abi.SectorID, ticket abi.SealRandomness, pieces []abi.PieceInfo) (storage.PreCommit1Out, error) {
+	defer t.tracker.track(sector, sealtasks.TTPreCommit1)()
+
+	return t.Worker.SealPreCommit1(ctx, sector, ticket, pieces)
+}
+
+func (t *trackedWorker) SealPreCommit2(ctx context.Context, sector abi.SectorID, pc1o storage.PreCommit1Out) (storage.SectorCids, error) {
+	defer t.tracker.track(sector, sealtasks.TTPreCommit2)()
+
+	return t.Worker.SealPreCommit2(ctx, sector, pc1o)
+}
+
+func (t *trackedWorker) SealCommit1(ctx context.Context, sector abi.SectorID, ticket abi.SealRandomness, seed abi.InteractiveSealRandomness, pieces []abi.PieceInfo, cids storage.SectorCids) (storage.Commit1Out, error) {
+	defer t.tracker.track(sector, sealtasks.TTCommit1)()
+
+	return t.Worker.SealCommit1(ctx, sector, ticket, seed, pieces, cids)
+}
+
+func (t *trackedWorker) SealCommit2(ctx context.Context, sector abi.SectorID, c1o storage.Commit1Out) (storage.Proof, error) {
+	defer t.tracker.track(sector, sealtasks.TTCommit2)()
+
+	return t.Worker.SealCommit2(ctx, sector, c1o)
+}
+
+func (t *trackedWorker) FinalizeSector(ctx context.Context, sector abi.SectorID, keepUnsealed []storage.Range) error {
+	defer t.tracker.track(sector, sealtasks.TTFinalize)()
+
+	return t.Worker.FinalizeSector(ctx, sector, keepUnsealed)
+}
+
+func (t *trackedWorker) AddPiece(ctx context.Context, sector abi.SectorID, pieceSizes []abi.UnpaddedPieceSize, newPieceSize abi.UnpaddedPieceSize, pieceData storage.Data) (abi.PieceInfo, error) {
+	defer t.tracker.track(sector, sealtasks.TTAddPiece)()
+
+	return t.Worker.AddPiece(ctx, sector, pieceSizes, newPieceSize, pieceData)
+}
+
+func (t *trackedWorker) Fetch(ctx context.Context, s abi.SectorID, ft stores.SectorFileType, ptype stores.PathType, am stores.AcquireMode) error {
+	defer t.tracker.track(s, sealtasks.TTFetch)()
+
+	return t.Worker.Fetch(ctx, s, ft, ptype, am)
+}
+
+func (t *trackedWorker) UnsealPiece(ctx context.Context, id abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize, randomness abi.SealRandomness, cid cid.Cid) error {
+	defer t.tracker.track(id, sealtasks.TTUnseal)()
+
+	return t.Worker.UnsealPiece(ctx, id, index, size, randomness, cid)
+}
+
+func (t *trackedWorker) ReadPiece(ctx context.Context, writer io.Writer, id abi.SectorID, index storiface.UnpaddedByteIndex, size abi.UnpaddedPieceSize) (bool, error) {
+	defer t.tracker.track(id, sealtasks.TTReadUnsealed)()
+
+	return t.Worker.ReadPiece(ctx, writer, id, index, size)
+}
+
+var _ Worker = &trackedWorker{}
diff --git a/zerocomm/zerocomm.go b/zerocomm/zerocomm.go
index 7d6308549..9b59723a0 100644
--- a/zerocomm/zerocomm.go
+++ b/zerocomm/zerocomm.go
@@ -51,5 +51,6 @@ var PieceComms = [Levels - Skip][32]byte{
 
 func ZeroPieceCommitment(sz abi.UnpaddedPieceSize) cid.Cid {
 	level := bits.TrailingZeros64(uint64(sz.Padded())) - Skip - 5 // 2^5 = 32
-	return commcid.PieceCommitmentV1ToCID(PieceComms[level][:])
+	commP, _ := commcid.PieceCommitmentV1ToCID(PieceComms[level][:])
+	return commP
 }