diff --git a/weed-fs/src/cmd/weed/master.go b/weed-fs/src/cmd/weed/master.go
index 6dc3b06b9..37d3b2295 100644
--- a/weed-fs/src/cmd/weed/master.go
+++ b/weed-fs/src/cmd/weed/master.go
@@ -5,7 +5,7 @@ import (
   "encoding/json"
   "log"
   "net/http"
-  "pkg/topology"
+  "pkg/storage"
   "strconv"
   "strings"
 )
@@ -39,7 +39,7 @@ func dirLookupHandler(w http.ResponseWriter, r *http.Request) {
     vid = vid[0:commaSep]
   }
   volumeId, _ := strconv.ParseUint(vid, 10, 64)
-  machine, e := mapper.Get(topology.VolumeId(volumeId))
+  machine, e := mapper.Get(storage.VolumeId(volumeId))
   if e == nil {
     writeJson(w, r, machine.Server)
   } else {
@@ -60,7 +60,7 @@ func dirAssignHandler(w http.ResponseWriter, r *http.Request) {
 func dirJoinHandler(w http.ResponseWriter, r *http.Request) {
   s := r.RemoteAddr[0:strings.Index(r.RemoteAddr, ":")+1] + r.FormValue("port")
   publicUrl := r.FormValue("publicUrl")
-  volumes := new([]topology.VolumeInfo)
+  volumes := new([]storage.VolumeInfo)
   json.Unmarshal([]byte(r.FormValue("volumes")), volumes)
   if *IsDebug {
     log.Println(s, "volumes", r.FormValue("volumes"))
diff --git a/weed-fs/src/pkg/directory/file_id.go b/weed-fs/src/pkg/directory/file_id.go
index be5388e61..723d94276 100644
--- a/weed-fs/src/pkg/directory/file_id.go
+++ b/weed-fs/src/pkg/directory/file_id.go
@@ -4,19 +4,18 @@ import (
 	"encoding/hex"
 	"log"
 	"pkg/storage"
-	"pkg/topology"
 	"strconv"
 	"strings"
 	"pkg/util"
 )
 
 type FileId struct {
-	VolumeId topology.VolumeId
+	VolumeId storage.VolumeId
 	Key      uint64
 	Hashcode uint32
 }
 
-func NewFileId(VolumeId topology.VolumeId, Key uint64, Hashcode uint32) *FileId {
+func NewFileId(VolumeId storage.VolumeId, Key uint64, Hashcode uint32) *FileId {
 	return &FileId{VolumeId: VolumeId, Key: Key, Hashcode: Hashcode}
 }
 func ParseFileId(fid string) *FileId{
@@ -28,7 +27,7 @@ func ParseFileId(fid string) *FileId{
 	vid_string, key_hash_string := a[0], a[1]
 	vid, _ := strconv.ParseUint(vid_string, 10, 64)
 	key, hash := storage.ParseKeyHash(key_hash_string)
-	return &FileId{VolumeId: topology.VolumeId(vid), Key: key, Hashcode: hash}
+	return &FileId{VolumeId: storage.VolumeId(vid), Key: key, Hashcode: hash}
 }
 func (n *FileId) String() string {
 	bytes := make([]byte, 12)
diff --git a/weed-fs/src/pkg/directory/volume_mapping.go b/weed-fs/src/pkg/directory/volume_mapping.go
index d48a6d12f..a6748f5c6 100644
--- a/weed-fs/src/pkg/directory/volume_mapping.go
+++ b/weed-fs/src/pkg/directory/volume_mapping.go
@@ -7,7 +7,7 @@ import (
 	"math/rand"
 	"os"
 	"path"
-	"pkg/topology"
+	"pkg/storage"
 	"strconv"
 	"sync"
 )
@@ -22,7 +22,7 @@ type MachineInfo struct {
 }
 type Machine struct {
 	Server  MachineInfo
-	Volumes []topology.VolumeInfo
+	Volumes []storage.VolumeInfo
 }
 
 type Mapper struct {
@@ -32,8 +32,8 @@ type Mapper struct {
 	volumeLock          sync.Mutex
   sequenceLock          sync.Mutex
 	Machines      []*Machine
-	vid2machineId map[topology.VolumeId]int //machineId is +1 of the index of []*Machine, to detect not found entries
-	Writers       []topology.VolumeId       // transient array of Writers volume id
+	vid2machineId map[storage.VolumeId]int //machineId is +1 of the index of []*Machine, to detect not found entries
+	Writers       []storage.VolumeId       // transient array of Writers volume id
 
 	FileIdSequence uint64
 	fileIdCounter  uint64
@@ -41,15 +41,15 @@ type Mapper struct {
 	volumeSizeLimit uint64
 }
 
-func NewMachine(server, publicUrl string, volumes []topology.VolumeInfo) *Machine {
+func NewMachine(server, publicUrl string, volumes []storage.VolumeInfo) *Machine {
 	return &Machine{Server: MachineInfo{Url: server, PublicUrl: publicUrl}, Volumes: volumes}
 }
 
 func NewMapper(dirname string, filename string, volumeSizeLimit uint64) (m *Mapper) {
 	m = &Mapper{dir: dirname, fileName: filename}
-	m.vid2machineId = make(map[topology.VolumeId]int)
+	m.vid2machineId = make(map[storage.VolumeId]int)
 	m.volumeSizeLimit = volumeSizeLimit
-	m.Writers = *new([]topology.VolumeId)
+	m.Writers = *new([]storage.VolumeId)
 	m.Machines = *new([]*Machine)
 
 	seqFile, se := os.OpenFile(path.Join(m.dir, m.fileName+".seq"), os.O_RDONLY, 0644)
@@ -102,7 +102,7 @@ func (m *Mapper) NextFileId(c string) (uint64,int) {
 	m.fileIdCounter = m.fileIdCounter - count
 	return m.FileIdSequence - m.fileIdCounter, int(count)
 }
-func (m *Mapper) Get(vid topology.VolumeId) (*Machine, error) {
+func (m *Mapper) Get(vid storage.VolumeId) (*Machine, error) {
 	machineId := m.vid2machineId[vid]
 	if machineId <= 0 {
 		return nil, errors.New("invalid volume id " + strconv.FormatUint(uint64(vid), 10))
@@ -134,7 +134,7 @@ func (m *Mapper) Add(machine Machine) {
 		m.vid2machineId[v.Id] = machineId + 1 //use base 1 indexed, to detect not found cases
 	}
 	//setting Writers, copy-on-write because of possible updating, this needs some future work!
-	var writers []topology.VolumeId
+	var writers []storage.VolumeId
 	for _, machine_entry := range m.Machines {
 		for _, v := range machine_entry.Volumes {
 			if uint64(v.Size) < m.volumeSizeLimit {
diff --git a/weed-fs/src/pkg/storage/store.go b/weed-fs/src/pkg/storage/store.go
index cd32a0ccf..ef7bc82fd 100644
--- a/weed-fs/src/pkg/storage/store.go
+++ b/weed-fs/src/pkg/storage/store.go
@@ -7,7 +7,6 @@ import (
 	"net/url"
 	"strconv"
 	"strings"
-	"pkg/topology"
 	"pkg/util"
 )
 
@@ -60,20 +59,20 @@ func (s *Store) addVolume(vid VolumeId) error {
 	s.volumes[vid] = NewVolume(s.dir, vid)
 	return nil
 }
-func (s *Store) Status() *[]*topology.VolumeInfo {
-	stats := new([]*topology.VolumeInfo)
+func (s *Store) Status() *[]*VolumeInfo {
+	stats := new([]*VolumeInfo)
 	for k, v := range s.volumes {
-		s := new(topology.VolumeInfo)
-		s.Id, s.Size = topology.VolumeId(k), v.Size()
+		s := new(VolumeInfo)
+		s.Id, s.Size = VolumeId(k), v.Size()
 		*stats = append(*stats, s)
 	}
 	return stats
 }
 func (s *Store) Join(mserver string) {
-	stats := new([]*topology.VolumeInfo)
+	stats := new([]*VolumeInfo)
 	for k, v := range s.volumes {
-		s := new(topology.VolumeInfo)
-		s.Id, s.Size = topology.VolumeId(k), v.Size()
+		s := new(VolumeInfo)
+		s.Id, s.Size = VolumeId(k), v.Size()
 		*stats = append(*stats, s)
 	}
 	bytes, _ := json.Marshal(stats)
diff --git a/weed-fs/src/pkg/storage/volume.go b/weed-fs/src/pkg/storage/volume.go
index 40e3eaaf4..55e389029 100644
--- a/weed-fs/src/pkg/storage/volume.go
+++ b/weed-fs/src/pkg/storage/volume.go
@@ -14,6 +14,10 @@ const (
 )
 
 type VolumeId uint32
+type VolumeInfo struct {
+  Id   VolumeId
+  Size int64
+}
 func NewVolumeId(vid string) (VolumeId,error) {
   volumeId, err := strconv.ParseUint(vid, 10, 64)
   return VolumeId(volumeId), err
diff --git a/weed-fs/src/pkg/topology/node.go b/weed-fs/src/pkg/topology/node.go
index 91f9a1373..4eccdbf65 100644
--- a/weed-fs/src/pkg/topology/node.go
+++ b/weed-fs/src/pkg/topology/node.go
@@ -1,15 +1,12 @@
 package topology
 
-import ()
+import (
+  "pkg/storage"
+)
 
 type NodeId uint32
-type VolumeId uint32
-type VolumeInfo struct {
-	Id   VolumeId
-	Size int64
-}
 type Node struct {
-	volumes     map[VolumeId]VolumeInfo
+	volumes     map[storage.VolumeId]storage.VolumeInfo
 	volumeLimit int
 	Ip          string
 	Port        int