diff --git a/weed/storage/volume_read.go b/weed/storage/volume_read.go
new file mode 100644
index 000000000..31dd3c784
--- /dev/null
+++ b/weed/storage/volume_read.go
@@ -0,0 +1,123 @@
+package storage
+
+import (
+	"fmt"
+	"io"
+	"time"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/chrislusf/seaweedfs/weed/storage/backend"
+	"github.com/chrislusf/seaweedfs/weed/storage/needle"
+	"github.com/chrislusf/seaweedfs/weed/storage/super_block"
+	. "github.com/chrislusf/seaweedfs/weed/storage/types"
+)
+
+// read fills in Needle content by looking up n.Id from NeedleMapper
+func (v *Volume) readNeedle(n *needle.Needle, readOption *ReadOption) (int, error) {
+	v.dataFileAccessLock.RLock()
+	defer v.dataFileAccessLock.RUnlock()
+
+	nv, ok := v.nm.Get(n.Id)
+	if !ok || nv.Offset.IsZero() {
+		return -1, ErrorNotFound
+	}
+	readSize := nv.Size
+	if readSize.IsDeleted() {
+		if readOption != nil && readOption.ReadDeleted && readSize != TombstoneFileSize {
+			glog.V(3).Infof("reading deleted %s", n.String())
+			readSize = -readSize
+		} else {
+			return -1, ErrorDeleted
+		}
+	}
+	if readSize == 0 {
+		return 0, nil
+	}
+	err := n.ReadData(v.DataBackend, nv.Offset.ToActualOffset(), readSize, v.Version())
+	if err == needle.ErrorSizeMismatch && OffsetSize == 4 {
+		err = n.ReadData(v.DataBackend, nv.Offset.ToActualOffset()+int64(MaxPossibleVolumeSize), readSize, v.Version())
+	}
+	v.checkReadWriteError(err)
+	if err != nil {
+		return 0, err
+	}
+	bytesRead := len(n.Data)
+	if !n.HasTtl() {
+		return bytesRead, nil
+	}
+	ttlMinutes := n.Ttl.Minutes()
+	if ttlMinutes == 0 {
+		return bytesRead, nil
+	}
+	if !n.HasLastModifiedDate() {
+		return bytesRead, nil
+	}
+	if time.Now().Before(time.Unix(0, int64(n.AppendAtNs)).Add(time.Duration(ttlMinutes) * time.Minute)) {
+		return bytesRead, nil
+	}
+	return -1, ErrorNotFound
+}
+
+type VolumeFileScanner interface {
+	VisitSuperBlock(super_block.SuperBlock) error
+	ReadNeedleBody() bool
+	VisitNeedle(n *needle.Needle, offset int64, needleHeader, needleBody []byte) error
+}
+
+func ScanVolumeFile(dirname string, collection string, id needle.VolumeId,
+	needleMapKind NeedleMapKind,
+	volumeFileScanner VolumeFileScanner) (err error) {
+	var v *Volume
+	if v, err = loadVolumeWithoutIndex(dirname, collection, id, needleMapKind); err != nil {
+		return fmt.Errorf("failed to load volume %d: %v", id, err)
+	}
+	if err = volumeFileScanner.VisitSuperBlock(v.SuperBlock); err != nil {
+		return fmt.Errorf("failed to process volume %d super block: %v", id, err)
+	}
+	defer v.Close()
+
+	version := v.Version()
+
+	offset := int64(v.SuperBlock.BlockSize())
+
+	return ScanVolumeFileFrom(version, v.DataBackend, offset, volumeFileScanner)
+}
+
+func ScanVolumeFileFrom(version needle.Version, datBackend backend.BackendStorageFile, offset int64, volumeFileScanner VolumeFileScanner) (err error) {
+	n, nh, rest, e := needle.ReadNeedleHeader(datBackend, version, offset)
+	if e != nil {
+		if e == io.EOF {
+			return nil
+		}
+		return fmt.Errorf("cannot read %s at offset %d: %v", datBackend.Name(), offset, e)
+	}
+	for n != nil {
+		var needleBody []byte
+		if volumeFileScanner.ReadNeedleBody() {
+			// println("needle", n.Id.String(), "offset", offset, "size", n.Size, "rest", rest)
+			if needleBody, err = n.ReadNeedleBody(datBackend, version, offset+NeedleHeaderSize, rest); err != nil {
+				glog.V(0).Infof("cannot read needle head [%d, %d) body [%d, %d) body length %d: %v", offset, offset+NeedleHeaderSize, offset+NeedleHeaderSize, offset+NeedleHeaderSize+rest, rest, err)
+				// err = fmt.Errorf("cannot read needle body: %v", err)
+				// return
+			}
+		}
+		err := volumeFileScanner.VisitNeedle(n, offset, nh, needleBody)
+		if err == io.EOF {
+			return nil
+		}
+		if err != nil {
+			glog.V(0).Infof("visit needle error: %v", err)
+			return fmt.Errorf("visit needle error: %v", err)
+		}
+		offset += NeedleHeaderSize + rest
+		glog.V(4).Infof("==> new entry offset %d", offset)
+		if n, nh, rest, err = needle.ReadNeedleHeader(datBackend, version, offset); err != nil {
+			if err == io.EOF {
+				return nil
+			}
+			return fmt.Errorf("cannot read needle header at offset %d: %v", offset, err)
+		}
+		glog.V(4).Infof("new entry needle size:%d rest:%d", n.Size, rest)
+	}
+	return nil
+}
diff --git a/weed/storage/volume_read_write.go b/weed/storage/volume_write.go
similarity index 71%
rename from weed/storage/volume_read_write.go
rename to weed/storage/volume_write.go
index 5251e09c0..c3cb813fb 100644
--- a/weed/storage/volume_read_write.go
+++ b/weed/storage/volume_write.go
@@ -4,14 +4,12 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
-	"io"
 	"os"
 	"time"
 
 	"github.com/chrislusf/seaweedfs/weed/glog"
 	"github.com/chrislusf/seaweedfs/weed/storage/backend"
 	"github.com/chrislusf/seaweedfs/weed/storage/needle"
-	"github.com/chrislusf/seaweedfs/weed/storage/super_block"
 	. "github.com/chrislusf/seaweedfs/weed/storage/types"
 )
 
@@ -227,52 +225,6 @@ func (v *Volume) doDeleteRequest(n *needle.Needle) (Size, error) {
 	return 0, nil
 }
 
-// read fills in Needle content by looking up n.Id from NeedleMapper
-func (v *Volume) readNeedle(n *needle.Needle, readOption *ReadOption) (int, error) {
-	v.dataFileAccessLock.RLock()
-	defer v.dataFileAccessLock.RUnlock()
-
-	nv, ok := v.nm.Get(n.Id)
-	if !ok || nv.Offset.IsZero() {
-		return -1, ErrorNotFound
-	}
-	readSize := nv.Size
-	if readSize.IsDeleted() {
-		if readOption != nil && readOption.ReadDeleted && readSize != TombstoneFileSize {
-			glog.V(3).Infof("reading deleted %s", n.String())
-			readSize = -readSize
-		} else {
-			return -1, ErrorDeleted
-		}
-	}
-	if readSize == 0 {
-		return 0, nil
-	}
-	err := n.ReadData(v.DataBackend, nv.Offset.ToActualOffset(), readSize, v.Version())
-	if err == needle.ErrorSizeMismatch && OffsetSize == 4 {
-		err = n.ReadData(v.DataBackend, nv.Offset.ToActualOffset()+int64(MaxPossibleVolumeSize), readSize, v.Version())
-	}
-	v.checkReadWriteError(err)
-	if err != nil {
-		return 0, err
-	}
-	bytesRead := len(n.Data)
-	if !n.HasTtl() {
-		return bytesRead, nil
-	}
-	ttlMinutes := n.Ttl.Minutes()
-	if ttlMinutes == 0 {
-		return bytesRead, nil
-	}
-	if !n.HasLastModifiedDate() {
-		return bytesRead, nil
-	}
-	if time.Now().Before(time.Unix(0, int64(n.AppendAtNs)).Add(time.Duration(ttlMinutes) * time.Minute)) {
-		return bytesRead, nil
-	}
-	return -1, ErrorNotFound
-}
-
 func (v *Volume) startWorker() {
 	go func() {
 		chanClosed := false
@@ -347,67 +299,3 @@ func (v *Volume) startWorker() {
 		}
 	}()
 }
-
-type VolumeFileScanner interface {
-	VisitSuperBlock(super_block.SuperBlock) error
-	ReadNeedleBody() bool
-	VisitNeedle(n *needle.Needle, offset int64, needleHeader, needleBody []byte) error
-}
-
-func ScanVolumeFile(dirname string, collection string, id needle.VolumeId,
-	needleMapKind NeedleMapKind,
-	volumeFileScanner VolumeFileScanner) (err error) {
-	var v *Volume
-	if v, err = loadVolumeWithoutIndex(dirname, collection, id, needleMapKind); err != nil {
-		return fmt.Errorf("failed to load volume %d: %v", id, err)
-	}
-	if err = volumeFileScanner.VisitSuperBlock(v.SuperBlock); err != nil {
-		return fmt.Errorf("failed to process volume %d super block: %v", id, err)
-	}
-	defer v.Close()
-
-	version := v.Version()
-
-	offset := int64(v.SuperBlock.BlockSize())
-
-	return ScanVolumeFileFrom(version, v.DataBackend, offset, volumeFileScanner)
-}
-
-func ScanVolumeFileFrom(version needle.Version, datBackend backend.BackendStorageFile, offset int64, volumeFileScanner VolumeFileScanner) (err error) {
-	n, nh, rest, e := needle.ReadNeedleHeader(datBackend, version, offset)
-	if e != nil {
-		if e == io.EOF {
-			return nil
-		}
-		return fmt.Errorf("cannot read %s at offset %d: %v", datBackend.Name(), offset, e)
-	}
-	for n != nil {
-		var needleBody []byte
-		if volumeFileScanner.ReadNeedleBody() {
-			// println("needle", n.Id.String(), "offset", offset, "size", n.Size, "rest", rest)
-			if needleBody, err = n.ReadNeedleBody(datBackend, version, offset+NeedleHeaderSize, rest); err != nil {
-				glog.V(0).Infof("cannot read needle head [%d, %d) body [%d, %d) body length %d: %v", offset, offset+NeedleHeaderSize, offset+NeedleHeaderSize, offset+NeedleHeaderSize+rest, rest, err)
-				// err = fmt.Errorf("cannot read needle body: %v", err)
-				// return
-			}
-		}
-		err := volumeFileScanner.VisitNeedle(n, offset, nh, needleBody)
-		if err == io.EOF {
-			return nil
-		}
-		if err != nil {
-			glog.V(0).Infof("visit needle error: %v", err)
-			return fmt.Errorf("visit needle error: %v", err)
-		}
-		offset += NeedleHeaderSize + rest
-		glog.V(4).Infof("==> new entry offset %d", offset)
-		if n, nh, rest, err = needle.ReadNeedleHeader(datBackend, version, offset); err != nil {
-			if err == io.EOF {
-				return nil
-			}
-			return fmt.Errorf("cannot read needle header at offset %d: %v", offset, err)
-		}
-		glog.V(4).Infof("new entry needle size:%d rest:%d", n.Size, rest)
-	}
-	return nil
-}