diff --git a/weed/command/backup.go b/weed/command/backup.go
index 86391f9c4..9c0bcbc52 100644
--- a/weed/command/backup.go
+++ b/weed/command/backup.go
@@ -88,7 +88,32 @@ func runBackup(cmd *Command, args []string) bool {
 		return true
 	}
 
-	if err := v.Synchronize(volumeServer, grpcDialOption); err != nil {
+	if v.SuperBlock.CompactRevision < uint16(stats.CompactRevision) {
+		if err = v.Compact(0); err != nil {
+			fmt.Printf("Compact Volume before synchronizing %v\n", err)
+			return true
+		}
+		if err = v.CommitCompact(); err != nil {
+			fmt.Printf("Commit Compact before synchronizing %v\n", err)
+			return true
+		}
+		v.SuperBlock.CompactRevision = uint16(stats.CompactRevision)
+		v.DataFile().WriteAt(v.SuperBlock.Bytes(),0)
+	}
+
+	if uint64(v.Size()) > stats.TailOffset {
+		// remove the old data
+		v.Destroy()
+		// recreate an empty volume
+		v, err = storage.NewVolume(*s.dir, *s.collection, vid, storage.NeedleMapInMemory, replication, ttl, 0)
+		if err != nil {
+			fmt.Printf("Error creating or reading from volume %d: %v\n", vid, err)
+			return true
+		}
+	}
+	defer v.Close()
+
+	if err := v.Follow(volumeServer, grpcDialOption); err != nil {
 		fmt.Printf("Error synchronizing volume %d: %v\n", vid, err)
 		return true
 	}
diff --git a/weed/pb/volume_server.proto b/weed/pb/volume_server.proto
index 93db5b981..7686cc614 100644
--- a/weed/pb/volume_server.proto
+++ b/weed/pb/volume_server.proto
@@ -24,6 +24,8 @@ service VolumeServer {
 
     rpc VolumeSyncStatus (VolumeSyncStatusRequest) returns (VolumeSyncStatusResponse) {
     }
+    rpc VolumeFollow (VolumeFollowRequest) returns (stream VolumeFollowResponse) {
+    }
     rpc VolumeSyncIndex (VolumeSyncIndexRequest) returns (stream VolumeSyncIndexResponse) {
     }
     rpc VolumeSyncData (VolumeSyncDataRequest) returns (stream VolumeSyncDataResponse) {
@@ -119,6 +121,14 @@ message VolumeSyncStatusResponse {
     uint64 idx_file_size = 8;
 }
 
+message VolumeFollowRequest {
+    uint32 volume_id = 1;
+    uint64 since = 2;
+}
+message VolumeFollowResponse {
+    bytes file_content = 1;
+}
+
 message VolumeSyncIndexRequest {
     uint32 volume_id = 1;
 }
diff --git a/weed/pb/volume_server_pb/volume_server.pb.go b/weed/pb/volume_server_pb/volume_server.pb.go
index d84a5b099..4c5f1effa 100644
--- a/weed/pb/volume_server_pb/volume_server.pb.go
+++ b/weed/pb/volume_server_pb/volume_server.pb.go
@@ -27,6 +27,8 @@ It has these top-level messages:
 	AssignVolumeResponse
 	VolumeSyncStatusRequest
 	VolumeSyncStatusResponse
+	VolumeFollowRequest
+	VolumeFollowResponse
 	VolumeSyncIndexRequest
 	VolumeSyncIndexResponse
 	VolumeSyncDataRequest
@@ -420,6 +422,46 @@ func (m *VolumeSyncStatusResponse) GetIdxFileSize() uint64 {
 	return 0
 }
 
+type VolumeFollowRequest struct {
+	VolumeId uint32 `protobuf:"varint,1,opt,name=volume_id,json=volumeId" json:"volume_id,omitempty"`
+	Since    uint64 `protobuf:"varint,2,opt,name=since" json:"since,omitempty"`
+}
+
+func (m *VolumeFollowRequest) Reset()                    { *m = VolumeFollowRequest{} }
+func (m *VolumeFollowRequest) String() string            { return proto.CompactTextString(m) }
+func (*VolumeFollowRequest) ProtoMessage()               {}
+func (*VolumeFollowRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{18} }
+
+func (m *VolumeFollowRequest) GetVolumeId() uint32 {
+	if m != nil {
+		return m.VolumeId
+	}
+	return 0
+}
+
+func (m *VolumeFollowRequest) GetSince() uint64 {
+	if m != nil {
+		return m.Since
+	}
+	return 0
+}
+
+type VolumeFollowResponse struct {
+	FileContent []byte `protobuf:"bytes,1,opt,name=file_content,json=fileContent,proto3" json:"file_content,omitempty"`
+}
+
+func (m *VolumeFollowResponse) Reset()                    { *m = VolumeFollowResponse{} }
+func (m *VolumeFollowResponse) String() string            { return proto.CompactTextString(m) }
+func (*VolumeFollowResponse) ProtoMessage()               {}
+func (*VolumeFollowResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{19} }
+
+func (m *VolumeFollowResponse) GetFileContent() []byte {
+	if m != nil {
+		return m.FileContent
+	}
+	return nil
+}
+
 type VolumeSyncIndexRequest struct {
 	VolumeId uint32 `protobuf:"varint,1,opt,name=volume_id,json=volumeId" json:"volume_id,omitempty"`
 }
@@ -427,7 +469,7 @@ type VolumeSyncIndexRequest struct {
 func (m *VolumeSyncIndexRequest) Reset()                    { *m = VolumeSyncIndexRequest{} }
 func (m *VolumeSyncIndexRequest) String() string            { return proto.CompactTextString(m) }
 func (*VolumeSyncIndexRequest) ProtoMessage()               {}
-func (*VolumeSyncIndexRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{18} }
+func (*VolumeSyncIndexRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{20} }
 
 func (m *VolumeSyncIndexRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -443,7 +485,7 @@ type VolumeSyncIndexResponse struct {
 func (m *VolumeSyncIndexResponse) Reset()                    { *m = VolumeSyncIndexResponse{} }
 func (m *VolumeSyncIndexResponse) String() string            { return proto.CompactTextString(m) }
 func (*VolumeSyncIndexResponse) ProtoMessage()               {}
-func (*VolumeSyncIndexResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{19} }
+func (*VolumeSyncIndexResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{21} }
 
 func (m *VolumeSyncIndexResponse) GetIndexFileContent() []byte {
 	if m != nil {
@@ -463,7 +505,7 @@ type VolumeSyncDataRequest struct {
 func (m *VolumeSyncDataRequest) Reset()                    { *m = VolumeSyncDataRequest{} }
 func (m *VolumeSyncDataRequest) String() string            { return proto.CompactTextString(m) }
 func (*VolumeSyncDataRequest) ProtoMessage()               {}
-func (*VolumeSyncDataRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{20} }
+func (*VolumeSyncDataRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{22} }
 
 func (m *VolumeSyncDataRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -507,7 +549,7 @@ type VolumeSyncDataResponse struct {
 func (m *VolumeSyncDataResponse) Reset()                    { *m = VolumeSyncDataResponse{} }
 func (m *VolumeSyncDataResponse) String() string            { return proto.CompactTextString(m) }
 func (*VolumeSyncDataResponse) ProtoMessage()               {}
-func (*VolumeSyncDataResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{21} }
+func (*VolumeSyncDataResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{23} }
 
 func (m *VolumeSyncDataResponse) GetFileContent() []byte {
 	if m != nil {
@@ -523,7 +565,7 @@ type VolumeMountRequest struct {
 func (m *VolumeMountRequest) Reset()                    { *m = VolumeMountRequest{} }
 func (m *VolumeMountRequest) String() string            { return proto.CompactTextString(m) }
 func (*VolumeMountRequest) ProtoMessage()               {}
-func (*VolumeMountRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{22} }
+func (*VolumeMountRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{24} }
 
 func (m *VolumeMountRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -538,7 +580,7 @@ type VolumeMountResponse struct {
 func (m *VolumeMountResponse) Reset()                    { *m = VolumeMountResponse{} }
 func (m *VolumeMountResponse) String() string            { return proto.CompactTextString(m) }
 func (*VolumeMountResponse) ProtoMessage()               {}
-func (*VolumeMountResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{23} }
+func (*VolumeMountResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{25} }
 
 type VolumeUnmountRequest struct {
 	VolumeId uint32 `protobuf:"varint,1,opt,name=volume_id,json=volumeId" json:"volume_id,omitempty"`
@@ -547,7 +589,7 @@ type VolumeUnmountRequest struct {
 func (m *VolumeUnmountRequest) Reset()                    { *m = VolumeUnmountRequest{} }
 func (m *VolumeUnmountRequest) String() string            { return proto.CompactTextString(m) }
 func (*VolumeUnmountRequest) ProtoMessage()               {}
-func (*VolumeUnmountRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{24} }
+func (*VolumeUnmountRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{26} }
 
 func (m *VolumeUnmountRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -562,7 +604,7 @@ type VolumeUnmountResponse struct {
 func (m *VolumeUnmountResponse) Reset()                    { *m = VolumeUnmountResponse{} }
 func (m *VolumeUnmountResponse) String() string            { return proto.CompactTextString(m) }
 func (*VolumeUnmountResponse) ProtoMessage()               {}
-func (*VolumeUnmountResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{25} }
+func (*VolumeUnmountResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{27} }
 
 type VolumeDeleteRequest struct {
 	VolumeId uint32 `protobuf:"varint,1,opt,name=volume_id,json=volumeId" json:"volume_id,omitempty"`
@@ -571,7 +613,7 @@ type VolumeDeleteRequest struct {
 func (m *VolumeDeleteRequest) Reset()                    { *m = VolumeDeleteRequest{} }
 func (m *VolumeDeleteRequest) String() string            { return proto.CompactTextString(m) }
 func (*VolumeDeleteRequest) ProtoMessage()               {}
-func (*VolumeDeleteRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{26} }
+func (*VolumeDeleteRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{28} }
 
 func (m *VolumeDeleteRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -586,7 +628,7 @@ type VolumeDeleteResponse struct {
 func (m *VolumeDeleteResponse) Reset()                    { *m = VolumeDeleteResponse{} }
 func (m *VolumeDeleteResponse) String() string            { return proto.CompactTextString(m) }
 func (*VolumeDeleteResponse) ProtoMessage()               {}
-func (*VolumeDeleteResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{27} }
+func (*VolumeDeleteResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{29} }
 
 type ReplicateVolumeRequest struct {
 	VolumeId       uint32 `protobuf:"varint,1,opt,name=volume_id,json=volumeId" json:"volume_id,omitempty"`
@@ -599,7 +641,7 @@ type ReplicateVolumeRequest struct {
 func (m *ReplicateVolumeRequest) Reset()                    { *m = ReplicateVolumeRequest{} }
 func (m *ReplicateVolumeRequest) String() string            { return proto.CompactTextString(m) }
 func (*ReplicateVolumeRequest) ProtoMessage()               {}
-func (*ReplicateVolumeRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{28} }
+func (*ReplicateVolumeRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{30} }
 
 func (m *ReplicateVolumeRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -642,7 +684,7 @@ type ReplicateVolumeResponse struct {
 func (m *ReplicateVolumeResponse) Reset()                    { *m = ReplicateVolumeResponse{} }
 func (m *ReplicateVolumeResponse) String() string            { return proto.CompactTextString(m) }
 func (*ReplicateVolumeResponse) ProtoMessage()               {}
-func (*ReplicateVolumeResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{29} }
+func (*ReplicateVolumeResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{31} }
 
 type CopyFileRequest struct {
 	VolumeId  uint32 `protobuf:"varint,1,opt,name=volume_id,json=volumeId" json:"volume_id,omitempty"`
@@ -653,7 +695,7 @@ type CopyFileRequest struct {
 func (m *CopyFileRequest) Reset()                    { *m = CopyFileRequest{} }
 func (m *CopyFileRequest) String() string            { return proto.CompactTextString(m) }
 func (*CopyFileRequest) ProtoMessage()               {}
-func (*CopyFileRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{30} }
+func (*CopyFileRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{32} }
 
 func (m *CopyFileRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -683,7 +725,7 @@ type CopyFileResponse struct {
 func (m *CopyFileResponse) Reset()                    { *m = CopyFileResponse{} }
 func (m *CopyFileResponse) String() string            { return proto.CompactTextString(m) }
 func (*CopyFileResponse) ProtoMessage()               {}
-func (*CopyFileResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{31} }
+func (*CopyFileResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{33} }
 
 func (m *CopyFileResponse) GetFileContent() []byte {
 	if m != nil {
@@ -699,7 +741,7 @@ type ReadVolumeFileStatusRequest struct {
 func (m *ReadVolumeFileStatusRequest) Reset()                    { *m = ReadVolumeFileStatusRequest{} }
 func (m *ReadVolumeFileStatusRequest) String() string            { return proto.CompactTextString(m) }
 func (*ReadVolumeFileStatusRequest) ProtoMessage()               {}
-func (*ReadVolumeFileStatusRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{32} }
+func (*ReadVolumeFileStatusRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{34} }
 
 func (m *ReadVolumeFileStatusRequest) GetVolumeId() uint32 {
 	if m != nil {
@@ -719,7 +761,7 @@ type ReadVolumeFileStatusResponse struct {
 func (m *ReadVolumeFileStatusResponse) Reset()                    { *m = ReadVolumeFileStatusResponse{} }
 func (m *ReadVolumeFileStatusResponse) String() string            { return proto.CompactTextString(m) }
 func (*ReadVolumeFileStatusResponse) ProtoMessage()               {}
-func (*ReadVolumeFileStatusResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{33} }
+func (*ReadVolumeFileStatusResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{35} }
 
 func (m *ReadVolumeFileStatusResponse) GetVolumeId() uint32 {
 	if m != nil {
@@ -766,7 +808,7 @@ type DiskStatus struct {
 func (m *DiskStatus) Reset()                    { *m = DiskStatus{} }
 func (m *DiskStatus) String() string            { return proto.CompactTextString(m) }
 func (*DiskStatus) ProtoMessage()               {}
-func (*DiskStatus) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{34} }
+func (*DiskStatus) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{36} }
 
 func (m *DiskStatus) GetDir() string {
 	if m != nil {
@@ -809,7 +851,7 @@ type MemStatus struct {
 func (m *MemStatus) Reset()                    { *m = MemStatus{} }
 func (m *MemStatus) String() string            { return proto.CompactTextString(m) }
 func (*MemStatus) ProtoMessage()               {}
-func (*MemStatus) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{35} }
+func (*MemStatus) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{37} }
 
 func (m *MemStatus) GetGoroutines() int32 {
 	if m != nil {
@@ -879,6 +921,8 @@ func init() {
 	proto.RegisterType((*AssignVolumeResponse)(nil), "volume_server_pb.AssignVolumeResponse")
 	proto.RegisterType((*VolumeSyncStatusRequest)(nil), "volume_server_pb.VolumeSyncStatusRequest")
 	proto.RegisterType((*VolumeSyncStatusResponse)(nil), "volume_server_pb.VolumeSyncStatusResponse")
+	proto.RegisterType((*VolumeFollowRequest)(nil), "volume_server_pb.VolumeFollowRequest")
+	proto.RegisterType((*VolumeFollowResponse)(nil), "volume_server_pb.VolumeFollowResponse")
 	proto.RegisterType((*VolumeSyncIndexRequest)(nil), "volume_server_pb.VolumeSyncIndexRequest")
 	proto.RegisterType((*VolumeSyncIndexResponse)(nil), "volume_server_pb.VolumeSyncIndexResponse")
 	proto.RegisterType((*VolumeSyncDataRequest)(nil), "volume_server_pb.VolumeSyncDataRequest")
@@ -919,6 +963,7 @@ type VolumeServerClient interface {
 	DeleteCollection(ctx context.Context, in *DeleteCollectionRequest, opts ...grpc.CallOption) (*DeleteCollectionResponse, error)
 	AssignVolume(ctx context.Context, in *AssignVolumeRequest, opts ...grpc.CallOption) (*AssignVolumeResponse, error)
 	VolumeSyncStatus(ctx context.Context, in *VolumeSyncStatusRequest, opts ...grpc.CallOption) (*VolumeSyncStatusResponse, error)
+	VolumeFollow(ctx context.Context, in *VolumeFollowRequest, opts ...grpc.CallOption) (VolumeServer_VolumeFollowClient, error)
 	VolumeSyncIndex(ctx context.Context, in *VolumeSyncIndexRequest, opts ...grpc.CallOption) (VolumeServer_VolumeSyncIndexClient, error)
 	VolumeSyncData(ctx context.Context, in *VolumeSyncDataRequest, opts ...grpc.CallOption) (VolumeServer_VolumeSyncDataClient, error)
 	VolumeMount(ctx context.Context, in *VolumeMountRequest, opts ...grpc.CallOption) (*VolumeMountResponse, error)
@@ -1009,8 +1054,40 @@ func (c *volumeServerClient) VolumeSyncStatus(ctx context.Context, in *VolumeSyn
 	return out, nil
 }
 
+func (c *volumeServerClient) VolumeFollow(ctx context.Context, in *VolumeFollowRequest, opts ...grpc.CallOption) (VolumeServer_VolumeFollowClient, error) {
+	stream, err := grpc.NewClientStream(ctx, &_VolumeServer_serviceDesc.Streams[0], c.cc, "/volume_server_pb.VolumeServer/VolumeFollow", opts...)
+	if err != nil {
+		return nil, err
+	}
+	x := &volumeServerVolumeFollowClient{stream}
+	if err := x.ClientStream.SendMsg(in); err != nil {
+		return nil, err
+	}
+	if err := x.ClientStream.CloseSend(); err != nil {
+		return nil, err
+	}
+	return x, nil
+}
+
+type VolumeServer_VolumeFollowClient interface {
+	Recv() (*VolumeFollowResponse, error)
+	grpc.ClientStream
+}
+
+type volumeServerVolumeFollowClient struct {
+	grpc.ClientStream
+}
+
+func (x *volumeServerVolumeFollowClient) Recv() (*VolumeFollowResponse, error) {
+	m := new(VolumeFollowResponse)
+	if err := x.ClientStream.RecvMsg(m); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
 func (c *volumeServerClient) VolumeSyncIndex(ctx context.Context, in *VolumeSyncIndexRequest, opts ...grpc.CallOption) (VolumeServer_VolumeSyncIndexClient, error) {
-	stream, err := grpc.NewClientStream(ctx, &_VolumeServer_serviceDesc.Streams[0], c.cc, "/volume_server_pb.VolumeServer/VolumeSyncIndex", opts...)
+	stream, err := grpc.NewClientStream(ctx, &_VolumeServer_serviceDesc.Streams[1], c.cc, "/volume_server_pb.VolumeServer/VolumeSyncIndex", opts...)
 	if err != nil {
 		return nil, err
 	}
@@ -1042,7 +1119,7 @@ func (x *volumeServerVolumeSyncIndexClient) Recv() (*VolumeSyncIndexResponse, er
 }
 
 func (c *volumeServerClient) VolumeSyncData(ctx context.Context, in *VolumeSyncDataRequest, opts ...grpc.CallOption) (VolumeServer_VolumeSyncDataClient, error) {
-	stream, err := grpc.NewClientStream(ctx, &_VolumeServer_serviceDesc.Streams[1], c.cc, "/volume_server_pb.VolumeServer/VolumeSyncData", opts...)
+	stream, err := grpc.NewClientStream(ctx, &_VolumeServer_serviceDesc.Streams[2], c.cc, "/volume_server_pb.VolumeServer/VolumeSyncData", opts...)
 	if err != nil {
 		return nil, err
 	}
@@ -1119,7 +1196,7 @@ func (c *volumeServerClient) ReadVolumeFileStatus(ctx context.Context, in *ReadV
 }
 
 func (c *volumeServerClient) CopyFile(ctx context.Context, in *CopyFileRequest, opts ...grpc.CallOption) (VolumeServer_CopyFileClient, error) {
-	stream, err := grpc.NewClientStream(ctx, &_VolumeServer_serviceDesc.Streams[2], c.cc, "/volume_server_pb.VolumeServer/CopyFile", opts...)
+	stream, err := grpc.NewClientStream(ctx, &_VolumeServer_serviceDesc.Streams[3], c.cc, "/volume_server_pb.VolumeServer/CopyFile", opts...)
 	if err != nil {
 		return nil, err
 	}
@@ -1162,6 +1239,7 @@ type VolumeServerServer interface {
 	DeleteCollection(context.Context, *DeleteCollectionRequest) (*DeleteCollectionResponse, error)
 	AssignVolume(context.Context, *AssignVolumeRequest) (*AssignVolumeResponse, error)
 	VolumeSyncStatus(context.Context, *VolumeSyncStatusRequest) (*VolumeSyncStatusResponse, error)
+	VolumeFollow(*VolumeFollowRequest, VolumeServer_VolumeFollowServer) error
 	VolumeSyncIndex(*VolumeSyncIndexRequest, VolumeServer_VolumeSyncIndexServer) error
 	VolumeSyncData(*VolumeSyncDataRequest, VolumeServer_VolumeSyncDataServer) error
 	VolumeMount(context.Context, *VolumeMountRequest) (*VolumeMountResponse, error)
@@ -1320,6 +1398,27 @@ func _VolumeServer_VolumeSyncStatus_Handler(srv interface{}, ctx context.Context
 	return interceptor(ctx, in, info, handler)
 }
 
+func _VolumeServer_VolumeFollow_Handler(srv interface{}, stream grpc.ServerStream) error {
+	m := new(VolumeFollowRequest)
+	if err := stream.RecvMsg(m); err != nil {
+		return err
+	}
+	return srv.(VolumeServerServer).VolumeFollow(m, &volumeServerVolumeFollowServer{stream})
+}
+
+type VolumeServer_VolumeFollowServer interface {
+	Send(*VolumeFollowResponse) error
+	grpc.ServerStream
+}
+
+type volumeServerVolumeFollowServer struct {
+	grpc.ServerStream
+}
+
+func (x *volumeServerVolumeFollowServer) Send(m *VolumeFollowResponse) error {
+	return x.ServerStream.SendMsg(m)
+}
+
 func _VolumeServer_VolumeSyncIndex_Handler(srv interface{}, stream grpc.ServerStream) error {
 	m := new(VolumeSyncIndexRequest)
 	if err := stream.RecvMsg(m); err != nil {
@@ -1531,6 +1630,11 @@ var _VolumeServer_serviceDesc = grpc.ServiceDesc{
 		},
 	},
 	Streams: []grpc.StreamDesc{
+		{
+			StreamName:    "VolumeFollow",
+			Handler:       _VolumeServer_VolumeFollow_Handler,
+			ServerStreams: true,
+		},
 		{
 			StreamName:    "VolumeSyncIndex",
 			Handler:       _VolumeServer_VolumeSyncIndex_Handler,
@@ -1553,83 +1657,86 @@ var _VolumeServer_serviceDesc = grpc.ServiceDesc{
 func init() { proto.RegisterFile("volume_server.proto", fileDescriptor0) }
 
 var fileDescriptor0 = []byte{
-	// 1247 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0xac, 0x58, 0x5b, 0x73, 0xdb, 0xc4,
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+	0x9b, 0x30, 0xb9, 0xdf, 0x48, 0xf6, 0x0f, 0x08, 0xe3, 0xfb, 0xf8, 0x09, 0xf4, 0xc6, 0xfe, 0xea,
+	0xdf, 0xad, 0xcf, 0x60, 0xd3, 0xa0, 0xc4, 0x56, 0x3d, 0xcf, 0xe7, 0x49, 0xfd, 0x99, 0xfb, 0xa7,
+	0x06, 0xb7, 0xab, 0x8d, 0xeb, 0xcc, 0x5d, 0xde, 0xdc, 0xc9, 0x5c, 0x63, 0xce, 0x88, 0x46, 0x8c,
+	0x8c, 0x02, 0x35, 0x8c, 0x7a, 0x6a, 0xb8, 0x7d, 0x9f, 0xc8, 0xcb, 0x53, 0xb0, 0x51, 0x9a, 0x82,
+	0x1c, 0x31, 0x39, 0x9f, 0x0c, 0x62, 0x53, 0x22, 0xda, 0xf2, 0x9c, 0x72, 0x88, 0xa9, 0xb6, 0x40,
+	0x6c, 0x49, 0x44, 0xa5, 0x28, 0xe6, 0xea, 0x0f, 0x00, 0x07, 0x4e, 0x74, 0x21, 0xd3, 0xe2, 0x37,
+	0xc5, 0x76, 0x42, 0xf5, 0x26, 0xf3, 0x25, 0x97, 0x10, 0xd7, 0x55, 0x41, 0xf3, 0x25, 0x9f, 0x0c,
+	0x71, 0x44, 0x6d, 0x15, 0x9e, 0x58, 0x73, 0xd9, 0x69, 0x48, 0xa9, 0x8a, 0x44, 0xac, 0xf1, 0x6f,
+	0x1a, 0x2c, 0x3c, 0xa7, 0x23, 0x85, 0xbc, 0x05, 0x70, 0xe6, 0x87, 0x7e, 0xcc, 0x1c, 0x8f, 0x46,
+	0xc2, 0x41, 0xcb, 0xc8, 0x48, 0xfe, 0xbd, 0x1f, 0x31, 0xa9, 0xa8, 0x7b, 0xaa, 0x92, 0x13, 0x6b,
+	0x2e, 0x3b, 0xa7, 0x24, 0x50, 0xcf, 0x92, 0x58, 0x8b, 0xd7, 0x80, 0x11, 0xeb, 0x42, 0xbc, 0x42,
+	0xfc, 0x35, 0xe0, 0x1f, 0x7b, 0xbf, 0x2c, 0x41, 0x57, 0xcd, 0x2d, 0x41, 0x77, 0xd1, 0x6b, 0xe8,
+	0x64, 0x68, 0x32, 0xfa, 0xa0, 0xcc, 0x86, 0xcb, 0xb4, 0x5b, 0xbf, 0x3b, 0x45, 0x4b, 0x75, 0xcc,
+	0x0c, 0xf2, 0xe0, 0x9d, 0x12, 0x0d, 0x45, 0x0f, 0xca, 0xd6, 0x93, 0x48, 0xae, 0xfe, 0xb0, 0x96,
+	0x6e, 0xea, 0x8f, 0xc1, 0x4a, 0x05, 0xaf, 0x44, 0x3b, 0x53, 0x50, 0x72, 0xdc, 0x56, 0x7f, 0x54,
+	0x53, 0x3b, 0xf5, 0xfa, 0x06, 0x50, 0x99, 0x74, 0xa2, 0x87, 0x53, 0x61, 0xc6, 0xa4, 0x56, 0xdf,
+	0xa9, 0xa7, 0x3c, 0x31, 0x51, 0x49, 0x47, 0xa7, 0x26, 0x9a, 0x23, 0xbc, 0x53, 0x13, 0x2d, 0x70,
+	0xdc, 0x19, 0x74, 0x01, 0xbd, 0x22, 0x55, 0x45, 0xdb, 0x93, 0x7e, 0x3f, 0x95, 0x98, 0xb0, 0xfe,
+	0xa0, 0x8e, 0x6a, 0xea, 0xcc, 0x84, 0x6e, 0x96, 0x50, 0xa2, 0x8a, 0x4b, 0x57, 0x41, 0x8d, 0xf5,
+	0x7b, 0xd3, 0xd4, 0xb2, 0xd9, 0x14, 0x09, 0x66, 0x55, 0x36, 0x13, 0xd8, 0x6b, 0x55, 0x36, 0x93,
+	0xf8, 0x2a, 0x9e, 0x41, 0x24, 0xe9, 0x3b, 0x49, 0xc3, 0xaa, 0xb2, 0xa9, 0x20, 0x7c, 0x55, 0xd9,
+	0x54, 0xb1, 0x39, 0x3c, 0xf3, 0x91, 0x86, 0x7e, 0x82, 0xe5, 0x02, 0xef, 0x42, 0xc3, 0x9b, 0x62,
+	0xcc, 0x32, 0x3a, 0x7d, 0xbb, 0x86, 0x66, 0xc6, 0xd7, 0x19, 0x2c, 0xe5, 0xe9, 0x0f, 0xba, 0x7f,
+	0x13, 0x40, 0x86, 0xbb, 0xe9, 0xc3, 0xe9, 0x8a, 0x19, 0x47, 0xaf, 0xa1, 0x93, 0xe1, 0x3d, 0x55,
+	0xf3, 0xa9, 0xcc, 0xa4, 0xf4, 0xbb, 0x53, 0xb4, 0xd2, 0xaa, 0x9c, 0xc0, 0x62, 0x8e, 0x09, 0xa1,
+	0x89, 0xe7, 0x9d, 0xe7, 0x57, 0xfa, 0xfd, 0xa9, 0x7a, 0xd9, 0x7b, 0x9c, 0x25, 0x48, 0x93, 0x2b,
+	0x9f, 0x9f, 0xb1, 0xf7, 0xa6, 0xa9, 0xa5, 0x0e, 0xce, 0x61, 0xb9, 0xc0, 0x59, 0xaa, 0xea, 0x5e,
+	0xcd, 0xc5, 0xaa, 0xea, 0x3e, 0x89, 0x00, 0xcd, 0xa0, 0xb7, 0xb0, 0x5a, 0x45, 0x0f, 0xd0, 0xa3,
+	0x2a, 0x90, 0x89, 0x1c, 0x44, 0xdf, 0xad, 0xab, 0x9e, 0x3a, 0x7e, 0x09, 0xed, 0x84, 0x0b, 0xa1,
+	0x3b, 0x65, 0xeb, 0x02, 0x2f, 0xd3, 0xf1, 0x4d, 0x2a, 0xe3, 0xcb, 0x75, 0x32, 0x27, 0xfe, 0x6d,
+	0x7a, 0xfc, 0x77, 0x00, 0x00, 0x00, 0xff, 0xff, 0x7d, 0xe2, 0xb6, 0x81, 0x84, 0x12, 0x00, 0x00,
 }
diff --git a/weed/server/volume_grpc_follow.go b/weed/server/volume_grpc_follow.go
new file mode 100644
index 000000000..bdd0ef6f5
--- /dev/null
+++ b/weed/server/volume_grpc_follow.go
@@ -0,0 +1,53 @@
+package weed_server
+
+import (
+	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/storage/types"
+	"io"
+	"os"
+
+	"github.com/chrislusf/seaweedfs/weed/pb/volume_server_pb"
+	"github.com/chrislusf/seaweedfs/weed/storage"
+)
+
+func (vs *VolumeServer) VolumeFollow(req *volume_server_pb.VolumeFollowRequest, stream volume_server_pb.VolumeServer_VolumeFollowServer) error {
+
+	v := vs.store.GetVolume(storage.VolumeId(req.VolumeId))
+	if v == nil {
+		return fmt.Errorf("not found volume id %d", req.VolumeId)
+	}
+
+	stopOffset := v.Size()
+	foundOffset, isLastOne, err := v.BinarySearchByAppendAtNs(req.Since)
+	if err != nil {
+		return fmt.Errorf("fail to locate by appendAtNs: %s", err)
+	}
+
+	if isLastOne {
+		return nil
+	}
+
+	startOffset := int64(foundOffset) * int64(types.NeedleEntrySize)
+
+	buf := make([]byte, 1024*1024*2)
+	return sendFileContent(v.DataFile(), buf, startOffset, stopOffset, stream)
+
+}
+
+func sendFileContent(datFile *os.File, buf []byte, startOffset, stopOffset int64, stream volume_server_pb.VolumeServer_VolumeFollowServer) error {
+	var blockSizeLimit = int64(len(buf))
+	for i := int64(0); i < stopOffset-startOffset; i += blockSizeLimit {
+		n, readErr := datFile.ReadAt(buf, startOffset+i)
+		if readErr == nil || readErr == io.EOF {
+			resp := &volume_server_pb.VolumeFollowResponse{}
+			resp.FileContent = buf[i : i+int64(n)]
+			sendErr := stream.Send(resp)
+			if sendErr != nil {
+				return sendErr
+			}
+		} else {
+			return readErr
+		}
+	}
+	return nil
+}
diff --git a/weed/storage/store_vacuum.go b/weed/storage/store_vacuum.go
index cc0521491..0036315c8 100644
--- a/weed/storage/store_vacuum.go
+++ b/weed/storage/store_vacuum.go
@@ -20,7 +20,7 @@ func (s *Store) CompactVolume(vid VolumeId, preallocate int64) error {
 }
 func (s *Store) CommitCompactVolume(vid VolumeId) error {
 	if v := s.findVolume(vid); v != nil {
-		return v.commitCompact()
+		return v.CommitCompact()
 	}
 	return fmt.Errorf("volume id %d is not found during commit compact", vid)
 }
diff --git a/weed/storage/volume_follow.go b/weed/storage/volume_follow.go
new file mode 100644
index 000000000..2aedd1682
--- /dev/null
+++ b/weed/storage/volume_follow.go
@@ -0,0 +1,220 @@
+package storage
+
+import (
+	"context"
+	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/operation"
+	"github.com/chrislusf/seaweedfs/weed/pb/volume_server_pb"
+	. "github.com/chrislusf/seaweedfs/weed/storage/types"
+	"google.golang.org/grpc"
+	"io"
+	"os"
+)
+
+// The volume sync with a master volume via 2 steps:
+// 1. The slave checks master side to find subscription checkpoint
+//	  to setup the replication.
+// 2. The slave receives the updates from master
+
+/*
+Assume the slave volume needs to follow the master volume.
+
+The master volume could be compacted, and could be many files ahead of
+slave volume.
+
+Step 0: // implemented in command/backup.go, to avoid dat file size overflow.
+0.1 If slave compact version is less than the master, do a local compaction, and set
+local compact version the same as the master.
+0.2 If the slave size is still bigger than the master, discard local copy and do a full copy.
+
+Step 1:
+The slave volume ask the master by the last modification time t.
+The master do a binary search in volume (use .idx as an array, and check the appendAtNs in .dat file),
+to find the first entry with appendAtNs > t.
+
+Step 2:
+The master send content bytes to the slave. The bytes are not chunked by needle.
+
+Step 3:
+The slave generate the needle map for the new bytes. (This may be optimized to incrementally
+update needle map when receiving new .dat bytes. But seems not necessary now.)
+
+*/
+
+func (v *Volume) Follow(volumeServer string, grpcDialOption grpc.DialOption) (error) {
+
+	ctx := context.Background()
+
+	startFromOffset := v.Size()
+	appendAtNs, err := v.findLastAppendAtNs()
+	if err != nil {
+		return err
+	}
+
+	err = operation.WithVolumeServerClient(volumeServer, grpcDialOption, func(client volume_server_pb.VolumeServerClient) error {
+
+		stream, err := client.VolumeFollow(ctx, &volume_server_pb.VolumeFollowRequest{
+			VolumeId: uint32(v.Id),
+			Since:    appendAtNs,
+		})
+		if err != nil {
+			return err
+		}
+
+		v.dataFile.Seek(startFromOffset, io.SeekStart)
+
+		for {
+			resp, recvErr := stream.Recv()
+			if recvErr != nil {
+				if recvErr == io.EOF {
+					break
+				} else {
+					return recvErr
+				}
+			}
+
+			_, writeErr := v.dataFile.Write(resp.FileContent)
+			if writeErr != nil {
+				return writeErr
+			}
+		}
+
+		return nil
+
+	})
+
+	if err != nil {
+		return err
+	}
+
+	// TODO add to needle map
+
+	return nil
+}
+
+func (v *Volume) findLastAppendAtNs() (uint64, error) {
+	offset, err := v.locateLastAppendEntry()
+	if err != nil {
+		return 0, err
+	}
+	if offset == 0 {
+		return 0, nil
+	}
+	return v.readAppendAtNs(offset)
+}
+
+func (v *Volume) locateLastAppendEntry() (Offset, error) {
+	indexFile, e := os.OpenFile(v.FileName()+".idx", os.O_RDONLY, 0644)
+	if e != nil {
+		return 0, fmt.Errorf("cannot read %s.idx: %v", v.FileName(), e)
+	}
+	defer indexFile.Close()
+
+	fi, err := indexFile.Stat()
+	if err != nil {
+		return 0, fmt.Errorf("file %s stat error: %v", indexFile.Name(), err)
+	}
+	fileSize := fi.Size()
+	if fileSize%NeedleEntrySize != 0 {
+		return 0, fmt.Errorf("unexpected file %s size: %d", indexFile.Name(), fileSize)
+	}
+	if fileSize == 0 {
+		return 0, nil
+	}
+
+	bytes := make([]byte, NeedleEntrySize)
+	n, e := indexFile.ReadAt(bytes, fileSize-NeedleEntrySize)
+	if n != NeedleEntrySize {
+		return 0, fmt.Errorf("file %s read error: %v", indexFile.Name(), e)
+	}
+	_, offset, _ := IdxFileEntry(bytes)
+
+	return offset, nil
+}
+
+func (v *Volume) readAppendAtNs(offset Offset) (uint64, error) {
+
+	n, bodyLength, err := ReadNeedleHeader(v.dataFile, v.SuperBlock.version, int64(offset)*NeedlePaddingSize)
+	if err != nil {
+		return 0, fmt.Errorf("ReadNeedleHeader: %v", err)
+	}
+	err = n.ReadNeedleBody(v.dataFile, v.SuperBlock.version, int64(offset)*NeedlePaddingSize, bodyLength)
+	if err != nil {
+		return 0, fmt.Errorf("ReadNeedleBody offset %d: %v", int64(offset)*NeedlePaddingSize, err)
+	}
+	return n.AppendAtNs, nil
+
+}
+
+// on server side
+func (v *Volume) BinarySearchByAppendAtNs(sinceNs uint64) (offset Offset, isLast bool, err error) {
+	indexFile, openErr := os.OpenFile(v.FileName()+".idx", os.O_RDONLY, 0644)
+	if openErr != nil {
+		err = fmt.Errorf("cannot read %s.idx: %v", v.FileName(), openErr)
+		return
+	}
+	defer indexFile.Close()
+
+	fi, statErr := indexFile.Stat()
+	if statErr != nil {
+		err = fmt.Errorf("file %s stat error: %v", indexFile.Name(), statErr)
+		return
+	}
+	fileSize := fi.Size()
+	if fileSize%NeedleEntrySize != 0 {
+		err = fmt.Errorf("unexpected file %s size: %d", indexFile.Name(), fileSize)
+		return
+	}
+
+	bytes := make([]byte, NeedleEntrySize)
+	entryCount := fileSize / NeedleEntrySize
+	l := int64(0)
+	h := entryCount
+
+	for l < h {
+
+		m := (l + h) / 2
+
+		if m == entryCount {
+			return 0, true, nil
+		}
+
+		// read the appendAtNs for entry m
+		offset, err = v.readAppendAtNsForIndexEntry(indexFile, bytes, m)
+		if err != nil {
+			return
+		}
+
+		mNs, nsReadErr := v.readAppendAtNs(offset)
+		if nsReadErr != nil {
+			err = nsReadErr
+			return
+		}
+
+		// move the boundary
+		if mNs <= sinceNs {
+			l = m + 1
+		} else {
+			h = m
+		}
+
+	}
+
+	if l == entryCount {
+		return 0, true, nil
+	}
+
+	offset, err = v.readAppendAtNsForIndexEntry(indexFile, bytes, l)
+
+	return offset, false, err
+
+}
+
+// bytes is of size NeedleEntrySize
+func (v *Volume) readAppendAtNsForIndexEntry(indexFile *os.File, bytes []byte, m int64) (Offset, error) {
+	if _, readErr := indexFile.ReadAt(bytes, m*NeedleEntrySize); readErr != nil && readErr != io.EOF {
+		return 0, readErr
+	}
+	_, offset, _ := IdxFileEntry(bytes)
+	return offset, nil
+}
diff --git a/weed/storage/volume_follow_test.go b/weed/storage/volume_follow_test.go
new file mode 100644
index 000000000..3291d203a
--- /dev/null
+++ b/weed/storage/volume_follow_test.go
@@ -0,0 +1,39 @@
+package storage
+
+import "testing"
+
+func TestBinarySearch(t *testing.T) {
+	var testInput []int
+	testInput = []int{-1, 0, 3, 5, 9, 12}
+
+	if 3 != binarySearchForLargerThanTarget(testInput, 4) {
+		t.Errorf("failed to find target %d", 4)
+	}
+	if 3 != binarySearchForLargerThanTarget(testInput, 3) {
+		t.Errorf("failed to find target %d", 3)
+	}
+	if 6 != binarySearchForLargerThanTarget(testInput, 12) {
+		t.Errorf("failed to find target %d", 12)
+	}
+	if 1 != binarySearchForLargerThanTarget(testInput, -1) {
+		t.Errorf("failed to find target %d", -1)
+	}
+	if 0 != binarySearchForLargerThanTarget(testInput, -2) {
+		t.Errorf("failed to find target %d", -2)
+	}
+
+}
+
+func binarySearchForLargerThanTarget(nums []int, target int) int {
+	l := 0
+	h := len(nums)
+	for l < h {
+		m := (l + h) / 2
+		if nums[m] <= target {
+			l = m + 1
+		} else {
+			h = m
+		}
+	}
+	return l
+}
diff --git a/weed/storage/volume_sync.go b/weed/storage/volume_sync.go
index 827e6685a..7e5432417 100644
--- a/weed/storage/volume_sync.go
+++ b/weed/storage/volume_sync.go
@@ -26,23 +26,17 @@ Assume the slave volume needs to follow the master volume.
 The master volume could be compacted, and could be many files ahead of
 slave volume.
 
-Step 1:
-The slave volume will ask the master volume for a snapshot
-of (existing file entries, last offset, number of compacted times).
-
-For each entry x in master existing file entries:
-  if x does not exist locally:
-    add x locally
+Step 0:
+If slave compact version is less than the master, do a local compaction.
+If the slave size is still less than the master, discard local copy and do a full copy.
 
-For each entry y in local slave existing file entries:
-  if y does not exist on master:
-    delete y locally
+Step 1:
+The slave volume ask the master by the last modification time t.
+The master do a binary search in volume (use .idx as an array, and check the appendAtNs in .dat file),
+to find the first entry with appendAtNs > t.
 
 Step 2:
-After this, use the last offset and number of compacted times to request
-the master volume to send a new file, and keep looping. If the number of
-compacted times is changed, go back to step 1 (very likely this can be
-optimized more later).
+The master iterate following entries (including the first one) and send it to the follower.
 
 */
 
@@ -58,7 +52,7 @@ func (v *Volume) Synchronize(volumeServer string, grpcDialOption grpc.DialOption
 			if err = v.Compact(0); err != nil {
 				return fmt.Errorf("Compact Volume before synchronizing %v", err)
 			}
-			if err = v.commitCompact(); err != nil {
+			if err = v.CommitCompact(); err != nil {
 				return fmt.Errorf("Commit Compact before synchronizing %v", err)
 			}
 		}
diff --git a/weed/storage/volume_vacuum.go b/weed/storage/volume_vacuum.go
index b29e15843..de39628db 100644
--- a/weed/storage/volume_vacuum.go
+++ b/weed/storage/volume_vacuum.go
@@ -38,7 +38,7 @@ func (v *Volume) Compact2() error {
 	return v.copyDataBasedOnIndexFile(filePath+".cpd", filePath+".cpx")
 }
 
-func (v *Volume) commitCompact() error {
+func (v *Volume) CommitCompact() error {
 	glog.V(0).Infof("Committing volume %d vacuuming...", v.Id)
 	v.dataFileAccessLock.Lock()
 	defer v.dataFileAccessLock.Unlock()
@@ -53,7 +53,7 @@ func (v *Volume) commitCompact() error {
 
 	var e error
 	if e = v.makeupDiff(v.FileName()+".cpd", v.FileName()+".cpx", v.FileName()+".dat", v.FileName()+".idx"); e != nil {
-		glog.V(0).Infof("makeupDiff in commitCompact volume %d failed %v", v.Id, e)
+		glog.V(0).Infof("makeupDiff in CommitCompact volume %d failed %v", v.Id, e)
 		e = os.Remove(v.FileName() + ".cpd")
 		if e != nil {
 			return e
diff --git a/weed/storage/volume_vacuum_test.go b/weed/storage/volume_vacuum_test.go
index 0bc24037d..4909885b9 100644
--- a/weed/storage/volume_vacuum_test.go
+++ b/weed/storage/volume_vacuum_test.go
@@ -85,7 +85,7 @@ func TestCompaction(t *testing.T) {
 		doSomeWritesDeletes(i+beforeCommitFileCount, v, t, infos)
 	}
 
-	v.commitCompact()
+	v.CommitCompact()
 
 	v.Close()