diff --git a/weed/server/volume_grpc_tier.go b/weed/server/volume_grpc_tier.go
index d3cdd62f2..ecf974642 100644
--- a/weed/server/volume_grpc_tier.go
+++ b/weed/server/volume_grpc_tier.go
@@ -64,7 +64,7 @@ func (vs *VolumeServer) VolumeTierCopyDatToRemote(req *volume_server_pb.VolumeTi
 	// copy the data file
 	key, size, err := backendStorage.CopyFile(diskFile.File, fn)
 	if err != nil {
-		return fmt.Errorf("backend %s copy file %s: %v", req.DestinationBackendName, diskFile.String(), err)
+		return fmt.Errorf("backend %s copy file %s: %v", req.DestinationBackendName, diskFile.Name(), err)
 	}
 
 	// save the remote file to volume tier info
diff --git a/weed/storage/backend/backend.go b/weed/storage/backend/backend.go
index 05a7fe84f..2f878110d 100644
--- a/weed/storage/backend/backend.go
+++ b/weed/storage/backend/backend.go
@@ -18,7 +18,7 @@ type BackendStorageFile interface {
 	Truncate(off int64) error
 	io.Closer
 	GetStat() (datSize int64, modTime time.Time, err error)
-	String() string
+	Name() string
 }
 
 type BackendStorage interface {
diff --git a/weed/storage/backend/disk_file.go b/weed/storage/backend/disk_file.go
index 4929f0573..c4b3caffb 100644
--- a/weed/storage/backend/disk_file.go
+++ b/weed/storage/backend/disk_file.go
@@ -45,10 +45,6 @@ func (df *DiskFile) GetStat() (datSize int64, modTime time.Time, err error) {
 	return 0, time.Time{}, err
 }
 
-func (df *DiskFile) String() string {
+func (df *DiskFile) Name() string {
 	return df.fullFilePath
 }
-
-func (df *DiskFile) Instantiate(src *os.File) error {
-	panic("should not implement Instantiate for DiskFile")
-}
diff --git a/weed/storage/backend/memory_map/memory_map_backend.go b/weed/storage/backend/memory_map/memory_map_backend.go
index f1d723c3b..03e7308d0 100644
--- a/weed/storage/backend/memory_map/memory_map_backend.go
+++ b/weed/storage/backend/memory_map/memory_map_backend.go
@@ -55,10 +55,6 @@ func (mmf *MemoryMappedFile) GetStat() (datSize int64, modTime time.Time, err er
 	return 0, time.Time{}, err
 }
 
-func (mmf *MemoryMappedFile) String() string {
+func (mmf *MemoryMappedFile) Name() string {
 	return mmf.mm.File.Name()
 }
-
-func (mmf *MemoryMappedFile) Instantiate(src *os.File) error {
-	panic("should not implement Instantiate for MemoryMappedFile")
-}
diff --git a/weed/storage/backend/s3_backend/s3_backend.go b/weed/storage/backend/s3_backend/s3_backend.go
index 458a9ca72..665f0b9b9 100644
--- a/weed/storage/backend/s3_backend/s3_backend.go
+++ b/weed/storage/backend/s3_backend/s3_backend.go
@@ -153,7 +153,6 @@ func (s3backendStorageFile S3BackendStorageFile) GetStat() (datSize int64, modTi
 	return
 }
 
-func (s3backendStorageFile S3BackendStorageFile) String() string {
+func (s3backendStorageFile S3BackendStorageFile) Name() string {
 	return s3backendStorageFile.key
 }
-
diff --git a/weed/storage/needle/needle_read_write.go b/weed/storage/needle/needle_read_write.go
index 60301fa36..7f8aa4823 100644
--- a/weed/storage/needle/needle_read_write.go
+++ b/weed/storage/needle/needle_read_write.go
@@ -131,7 +131,7 @@ func (n *Needle) Append(w backend.BackendStorageFile, version Version) (offset u
 		defer func(w backend.BackendStorageFile, off int64) {
 			if err != nil {
 				if te := w.Truncate(end); te != nil {
-					glog.V(0).Infof("Failed to truncate %s back to %d with error: %v", w.String(), end, te)
+					glog.V(0).Infof("Failed to truncate %s back to %d with error: %v", w.Name(), end, te)
 				}
 			}
 		}(w, end)
diff --git a/weed/storage/volume.go b/weed/storage/volume.go
index 7edcacebd..6fe90593d 100644
--- a/weed/storage/volume.go
+++ b/weed/storage/volume.go
@@ -83,7 +83,7 @@ func (v *Volume) FileStat() (datSize uint64, idxSize uint64, modTime time.Time)
 	if e == nil {
 		return uint64(datFileSize), v.nm.IndexFileSize(), modTime
 	}
-	glog.V(0).Infof("Failed to read file size %s %v", v.DataBackend.String(), e)
+	glog.V(0).Infof("Failed to read file size %s %v", v.DataBackend.Name(), e)
 	return // -1 causes integer overflow and the volume to become unwritable.
 }
 
diff --git a/weed/storage/volume_read_write.go b/weed/storage/volume_read_write.go
index 0f9f8a94b..e9f6175aa 100644
--- a/weed/storage/volume_read_write.go
+++ b/weed/storage/volume_read_write.go
@@ -59,7 +59,7 @@ func (v *Volume) Destroy() (err error) {
 func (v *Volume) writeNeedle(n *needle.Needle) (offset uint64, size uint32, isUnchanged bool, err error) {
 	glog.V(4).Infof("writing needle %s", needle.NewFileIdFromNeedle(v.Id, n).String())
 	if v.readOnly {
-		err = fmt.Errorf("%s is read-only", v.DataBackend.String())
+		err = fmt.Errorf("%s is read-only", v.DataBackend.Name())
 		return
 	}
 	v.dataFileAccessLock.Lock()
@@ -112,7 +112,7 @@ func (v *Volume) writeNeedle(n *needle.Needle) (offset uint64, size uint32, isUn
 func (v *Volume) deleteNeedle(n *needle.Needle) (uint32, error) {
 	glog.V(4).Infof("delete needle %s", needle.NewFileIdFromNeedle(v.Id, n).String())
 	if v.readOnly {
-		return 0, fmt.Errorf("%s is read-only", v.DataBackend.String())
+		return 0, fmt.Errorf("%s is read-only", v.DataBackend.Name())
 	}
 	v.dataFileAccessLock.Lock()
 	defer v.dataFileAccessLock.Unlock()
@@ -202,7 +202,7 @@ func ScanVolumeFileFrom(version needle.Version, datBackend backend.BackendStorag
 		if e == io.EOF {
 			return nil
 		}
-		return fmt.Errorf("cannot read %s at offset %d: %v", datBackend.String(), offset, e)
+		return fmt.Errorf("cannot read %s at offset %d: %v", datBackend.Name(), offset, e)
 	}
 	for n != nil {
 		var needleBody []byte
diff --git a/weed/storage/volume_super_block.go b/weed/storage/volume_super_block.go
index 911cd5455..6e5122190 100644
--- a/weed/storage/volume_super_block.go
+++ b/weed/storage/volume_super_block.go
@@ -78,7 +78,7 @@ func (v *Volume) maybeWriteSuperBlock() error {
 
 	datSize, _, e := v.DataBackend.GetStat()
 	if e != nil {
-		glog.V(0).Infof("failed to stat datafile %s: %v", v.DataBackend.String(), e)
+		glog.V(0).Infof("failed to stat datafile %s: %v", v.DataBackend.Name(), e)
 		return e
 	}
 	if datSize == 0 {
@@ -87,7 +87,7 @@ func (v *Volume) maybeWriteSuperBlock() error {
 		if e != nil && os.IsPermission(e) {
 			//read-only, but zero length - recreate it!
 			var dataFile *os.File
-			if dataFile, e = os.Create(v.DataBackend.String()); e == nil {
+			if dataFile, e = os.Create(v.DataBackend.Name()); e == nil {
 				v.DataBackend = backend.NewDiskFile(dataFile)
 				if _, e = v.DataBackend.WriteAt(v.SuperBlock.Bytes(), 0); e == nil {
 					v.readOnly = false
@@ -108,7 +108,7 @@ func ReadSuperBlock(datBackend backend.BackendStorageFile) (superBlock SuperBloc
 
 	header := make([]byte, _SuperBlockSize)
 	if _, e := datBackend.ReadAt(header, 0); e != nil {
-		err = fmt.Errorf("cannot read volume %s super block: %v", datBackend.String(), e)
+		err = fmt.Errorf("cannot read volume %s super block: %v", datBackend.Name(), e)
 		return
 	}
 
@@ -127,7 +127,7 @@ func ReadSuperBlock(datBackend backend.BackendStorageFile) (superBlock SuperBloc
 		superBlock.Extra = &master_pb.SuperBlockExtra{}
 		err = proto.Unmarshal(extraData, superBlock.Extra)
 		if err != nil {
-			err = fmt.Errorf("cannot read volume %s super block extra: %v", datBackend.String(), err)
+			err = fmt.Errorf("cannot read volume %s super block extra: %v", datBackend.Name(), err)
 			return
 		}
 	}
diff --git a/weed/util/queue.go b/weed/util/queue.go
index 31d9d1769..1e6211e0d 100644
--- a/weed/util/queue.go
+++ b/weed/util/queue.go
@@ -58,4 +58,4 @@ func (q *Queue) Dequeue() interface{} {
 	q.count--
 
 	return n.data
-}
\ No newline at end of file
+}