diff --git a/cmd/lotus-storage-miner/backup.go b/cmd/lotus-storage-miner/backup.go
index a1ad360c9..55604b6fb 100644
--- a/cmd/lotus-storage-miner/backup.go
+++ b/cmd/lotus-storage-miner/backup.go
@@ -60,7 +60,7 @@ func offlineBackup(cctx *cli.Context) error {
 		return xerrors.Errorf("repo at '%s' is not initialized", cctx.String(FlagMinerRepo))
 	}
 
-	lr, err := r.Lock(repo.StorageMiner)
+	lr, err := r.LockRO(repo.StorageMiner)
 	if err != nil {
 		return xerrors.Errorf("locking repo: %w", err)
 	}
diff --git a/node/repo/fsrepo.go b/node/repo/fsrepo.go
index a69cdd55d..c4571c478 100644
--- a/node/repo/fsrepo.go
+++ b/node/repo/fsrepo.go
@@ -226,11 +226,23 @@ func (fsr *FsRepo) Lock(repoType RepoType) (LockedRepo, error) {
 	}, nil
 }
 
+// Like Lock, except datastores will work in read-only mode
+func (fsr *FsRepo) LockRO(repoType RepoType) (LockedRepo, error) {
+	lr, err := fsr.Lock(repoType)
+	if err != nil {
+		return nil, err
+	}
+
+	lr.(*fsLockedRepo).readonly = true
+	return lr, nil
+}
+
 type fsLockedRepo struct {
 	path       string
 	configPath string
 	repoType   RepoType
 	closer     io.Closer
+	readonly   bool
 
 	ds     map[string]datastore.Batching
 	dsErr  error
diff --git a/node/repo/fsrepo_ds.go b/node/repo/fsrepo_ds.go
index f4afe0dee..aa91d2514 100644
--- a/node/repo/fsrepo_ds.go
+++ b/node/repo/fsrepo_ds.go
@@ -14,7 +14,7 @@ import (
 	ldbopts "github.com/syndtr/goleveldb/leveldb/opt"
 )
 
-type dsCtor func(path string) (datastore.Batching, error)
+type dsCtor func(path string, readonly bool) (datastore.Batching, error)
 
 var fsDatastores = map[string]dsCtor{
 	"chain":    chainBadgerDs,
@@ -26,9 +26,10 @@ var fsDatastores = map[string]dsCtor{
 	"client": badgerDs, // client specific
 }
 
-func chainBadgerDs(path string) (datastore.Batching, error) {
+func chainBadgerDs(path string, readonly bool) (datastore.Batching, error) {
 	opts := badger.DefaultOptions
 	opts.GcInterval = 0 // disable GC for chain datastore
+	opts.ReadOnly = readonly
 
 	opts.Options = dgbadger.DefaultOptions("").WithTruncate(true).
 		WithValueThreshold(1 << 10)
@@ -36,23 +37,26 @@ func chainBadgerDs(path string) (datastore.Batching, error) {
 	return badger.NewDatastore(path, &opts)
 }
 
-func badgerDs(path string) (datastore.Batching, error) {
+func badgerDs(path string, readonly bool) (datastore.Batching, error) {
 	opts := badger.DefaultOptions
+	opts.ReadOnly = readonly
+
 	opts.Options = dgbadger.DefaultOptions("").WithTruncate(true).
 		WithValueThreshold(1 << 10)
 
 	return badger.NewDatastore(path, &opts)
 }
 
-func levelDs(path string) (datastore.Batching, error) {
+func levelDs(path string, readonly bool) (datastore.Batching, error) {
 	return levelds.NewDatastore(path, &levelds.Options{
 		Compression: ldbopts.NoCompression,
 		NoSync:      false,
 		Strict:      ldbopts.StrictAll,
+		ReadOnly:    readonly,
 	})
 }
 
-func (fsr *fsLockedRepo) openDatastores() (map[string]datastore.Batching, error) {
+func (fsr *fsLockedRepo) openDatastores(readonly bool) (map[string]datastore.Batching, error) {
 	if err := os.MkdirAll(fsr.join(fsDatastore), 0755); err != nil {
 		return nil, xerrors.Errorf("mkdir %s: %w", fsr.join(fsDatastore), err)
 	}
@@ -63,7 +67,7 @@ func (fsr *fsLockedRepo) openDatastores() (map[string]datastore.Batching, error)
 		prefix := datastore.NewKey(p)
 
 		// TODO: optimization: don't init datastores we don't need
-		ds, err := ctor(fsr.join(filepath.Join(fsDatastore, p)))
+		ds, err := ctor(fsr.join(filepath.Join(fsDatastore, p)), readonly)
 		if err != nil {
 			return nil, xerrors.Errorf("opening datastore %s: %w", prefix, err)
 		}
@@ -78,7 +82,7 @@ func (fsr *fsLockedRepo) openDatastores() (map[string]datastore.Batching, error)
 
 func (fsr *fsLockedRepo) Datastore(ns string) (datastore.Batching, error) {
 	fsr.dsOnce.Do(func() {
-		fsr.ds, fsr.dsErr = fsr.openDatastores()
+		fsr.ds, fsr.dsErr = fsr.openDatastores(fsr.readonly)
 	})
 
 	if fsr.dsErr != nil {