diff --git a/weed-fs/src/cmd/weed/master.go b/weed-fs/src/cmd/weed/master.go
index 29b05efce..72c0d6f91 100644
--- a/weed-fs/src/cmd/weed/master.go
+++ b/weed-fs/src/cmd/weed/master.go
@@ -5,7 +5,9 @@ import (
 	"log"
 	"net/http"
 	"pkg/directory"
+	"pkg/replication"
 	"pkg/storage"
+	"pkg/topology"
 	"strconv"
 	"strings"
 	"time"
@@ -29,11 +31,14 @@ var (
 	mport             = cmdMaster.Flag.Int("port", 9333, "http listen port")
 	metaFolder        = cmdMaster.Flag.String("mdir", "/tmp", "data directory to store mappings")
 	capacity          = cmdMaster.Flag.Int("capacity", 100, "maximum number of volumes to hold")
-	mapper            *directory.Mapper
 	volumeSizeLimitMB = cmdMaster.Flag.Uint("volumeSizeLimitMB", 32*1024, "Default Volume Size in MegaBytes")
 	mpulse            = cmdMaster.Flag.Int("pulseSeconds", 5, "number of seconds between heartbeats")
 )
 
+var mapper *directory.Mapper
+var topo *topology.Topology
+var vg *replication.VolumeGrowth
+
 func dirLookupHandler(w http.ResponseWriter, r *http.Request) {
 	vid := r.FormValue("volumeId")
 	commaSep := strings.Index(vid, ",")
@@ -43,10 +48,10 @@ func dirLookupHandler(w http.ResponseWriter, r *http.Request) {
 	volumeId, _ := storage.NewVolumeId(vid)
 	machines, e := mapper.Get(volumeId)
 	if e == nil {
-	  ret:= []map[string]string{}
-	  for _, machine := range machines {
-	    ret = append(ret,map[string]string{"url": machine.Url, "publicUrl": machine.PublicUrl})
-	  }
+		ret := []map[string]string{}
+		for _, machine := range machines {
+			ret = append(ret, map[string]string{"url": machine.Url, "publicUrl": machine.PublicUrl})
+		}
 		writeJson(w, r, ret)
 	} else {
 		log.Println("Invalid volume id", volumeId)
@@ -62,7 +67,27 @@ func dirAssignHandler(w http.ResponseWriter, r *http.Request) {
 		writeJson(w, r, map[string]string{"error": err.Error()})
 	}
 }
+func dirAssign2Handler(w http.ResponseWriter, r *http.Request) {
+	c, _ := strconv.Atoi(r.FormValue("count"))
+	rt := storage.NewReplicationType(r.FormValue("replication"))
+	if topo.GetVolumeLayout(rt).GetActiveVolumeCount() <= 0 {
+		if topo.FreeSpace() <= 0 {
+			writeJson(w, r, map[string]string{"error": "No free volumes left!"})
+		} else {
+			vg.GrowByType(rt, topo)
+		}
+	}
+	fid, count, dn, err := topo.PickForWrite(rt, c)
+	if err == nil {
+		writeJson(w, r, map[string]interface{}{"fid": fid, "url": dn.Ip + ":" + strconv.Itoa(dn.Port), "publicUrl": dn.PublicUrl, "count": count})
+	} else {
+		writeJson(w, r, map[string]string{"error": err.Error()})
+	}
+}
 func dirJoinHandler(w http.ResponseWriter, r *http.Request) {
+	ip := r.RemoteAddr[0:strings.Index(r.RemoteAddr, ":")]
+	port, _ := strconv.Atoi(r.FormValue("port"))
+	maxVolumeCount, _ := strconv.Atoi(r.FormValue("maxVolumeCount"))
 	s := r.RemoteAddr[0:strings.Index(r.RemoteAddr, ":")+1] + r.FormValue("port")
 	publicUrl := r.FormValue("publicUrl")
 	volumes := new([]storage.VolumeInfo)
@@ -71,20 +96,40 @@ func dirJoinHandler(w http.ResponseWriter, r *http.Request) {
 		log.Println(s, "volumes", r.FormValue("volumes"))
 	}
 	mapper.Add(directory.NewMachine(s, publicUrl, *volumes, time.Now().Unix()))
+
+	//new ways
+	topo.RegisterVolumes(*volumes, ip, port, publicUrl, maxVolumeCount)
 }
-func dirStatusHandler(w http.ResponseWriter, r *http.Request) {
+func dirOldStatusHandler(w http.ResponseWriter, r *http.Request) {
 	writeJson(w, r, mapper)
 }
+func dirNewStatusHandler(w http.ResponseWriter, r *http.Request) {
+	writeJson(w, r, topo.ToMap())
+}
+func volumeGrowHandler(w http.ResponseWriter, r *http.Request) {
+	rt := storage.NewReplicationType(r.FormValue("replication"))
+	count, err := strconv.Atoi(r.FormValue("count"))
+	if err != nil {
+		vg.GrowByType(rt, topo)
+	} else {
+		vg.GrowByCountAndType(count, rt, topo)
+	}
+}
 
 func runMaster(cmd *Command, args []string) bool {
+	topo = topology.NewTopology("topo", *metaFolder, "toposequence", uint64(*volumeSizeLimitMB)*1024*1024, *mpulse)
+	vg = replication.NewDefaultVolumeGrowth()
 	log.Println("Volume Size Limit is", *volumeSizeLimitMB, "MB")
 	mapper = directory.NewMapper(*metaFolder, "directory", uint64(*volumeSizeLimitMB)*1024*1024, *mpulse)
 	http.HandleFunc("/dir/assign", dirAssignHandler)
+	http.HandleFunc("/dir/assign2", dirAssign2Handler)
 	http.HandleFunc("/dir/lookup", dirLookupHandler)
 	http.HandleFunc("/dir/join", dirJoinHandler)
-	http.HandleFunc("/dir/status", dirStatusHandler)
+	http.HandleFunc("/dir/status", dirOldStatusHandler)
+	http.HandleFunc("/dir/status2", dirNewStatusHandler) //temporary
+	http.HandleFunc("/vol/grow", volumeGrowHandler)
 
-  mapper.StartRefreshWritableVolumes()
+	mapper.StartRefreshWritableVolumes()
 
 	log.Println("Start directory service at http://127.0.0.1:" + strconv.Itoa(*mport))
 	e := http.ListenAndServe(":"+strconv.Itoa(*mport), nil)
diff --git a/weed-fs/src/cmd/weed/upload.go b/weed-fs/src/cmd/weed/upload.go
index 5cfb6ee97..8502ca417 100644
--- a/weed-fs/src/cmd/weed/upload.go
+++ b/weed-fs/src/cmd/weed/upload.go
@@ -39,19 +39,22 @@ type AssignResult struct {
   Error     string "error"
 }
 
-func assign(count int) (AssignResult, error) {
+func assign(count int) (*AssignResult, error) {
   values := make(url.Values)
   values.Add("count", strconv.Itoa(count))
-  jsonBlob := util.Post("http://"+*server+"/dir/assign", values)
+  jsonBlob, err := util.Post("http://"+*server+"/dir/assign", values)
+  if err != nil {
+    return nil, err
+  }
   var ret AssignResult
-  err := json.Unmarshal(jsonBlob, &ret)
+  err = json.Unmarshal(jsonBlob, &ret)
   if err != nil {
-    return ret, err
+    return nil, err
   }
   if ret.Count <= 0 {
-    return ret, errors.New(ret.Error)
+    return nil, errors.New(ret.Error)
   }
-  return ret, nil
+  return &ret, nil
 }
 
 type UploadResult struct {
diff --git a/weed-fs/src/cmd/weed/volume.go b/weed-fs/src/cmd/weed/volume.go
index 0b7ef9671..39faaffec 100644
--- a/weed-fs/src/cmd/weed/volume.go
+++ b/weed-fs/src/cmd/weed/volume.go
@@ -6,6 +6,7 @@ import (
 	"math/rand"
 	"mime"
 	"net/http"
+	"os"
 	"pkg/storage"
 	"strconv"
 	"strings"
@@ -18,7 +19,7 @@ func init() {
 }
 
 var cmdVolume = &Command{
-	UsageLine: "volume -port=8080 -dir=/tmp -volumes=0-99 -publicUrl=server_name:8080 -mserver=localhost:9333",
+	UsageLine: "volume -port=8080 -dir=/tmp -min=3 -max=5 -publicUrl=server_name:8080 -mserver=localhost:9333",
 	Short:     "start a volume server",
 	Long: `start a volume server to provide storage spaces
 
@@ -26,12 +27,13 @@ var cmdVolume = &Command{
 }
 
 var (
-	vport       = cmdVolume.Flag.Int("port", 8080, "http listen port")
-	chunkFolder = cmdVolume.Flag.String("dir", "/tmp", "data directory to store files")
-	volumes     = cmdVolume.Flag.String("volumes", "0,1-3,4", "comma-separated list of volume ids or range of ids")
-	publicUrl   = cmdVolume.Flag.String("publicUrl", "localhost:8080", "public url to serve data read")
-	masterNode  = cmdVolume.Flag.String("mserver", "localhost:9333", "master directory server to store mappings")
-	vpulse      = cmdVolume.Flag.Int("pulseSeconds", 5, "number of seconds between heartbeats")
+	vport          = cmdVolume.Flag.Int("port", 8080, "http listen port")
+	volumeFolder    = cmdVolume.Flag.String("dir", "/tmp", "data directory to store files")
+	volumes        = cmdVolume.Flag.String("volumes", "", "comma-separated list, or ranges of volume ids")
+	publicUrl      = cmdVolume.Flag.String("publicUrl", "localhost:8080", "public url to serve data read")
+	masterNode     = cmdVolume.Flag.String("mserver", "localhost:9333", "master directory server to store mappings")
+	vpulse         = cmdVolume.Flag.Int("pulseSeconds", 5, "number of seconds between heartbeats")
+	maxVolumeCount = cmdVolume.Flag.Int("maxVolumeCount", 5, "maximum number of volumes")
 
 	store *storage.Store
 )
@@ -46,9 +48,9 @@ func assignVolumeHandler(w http.ResponseWriter, r *http.Request) {
 	} else {
 		writeJson(w, r, map[string]string{"error": err.Error()})
 	}
-  if *IsDebug {
-    log.Println("volume =", r.FormValue("volume"), ", replicationType =", r.FormValue("replicationType"), ", error =", err)
-  }
+	if *IsDebug {
+		log.Println("volume =", r.FormValue("volume"), ", replicationType =", r.FormValue("replicationType"), ", error =", err)
+	}
 }
 func setVolumeLocationsHandler(w http.ResponseWriter, r *http.Request) {
 	if *IsDebug {
@@ -86,11 +88,15 @@ func GetHandler(w http.ResponseWriter, r *http.Request) {
 	}
 	cookie := n.Cookie
 	count, e := store.Read(volumeId, n)
+	if e != nil {
+    w.WriteHeader(404)
+	}
 	if *IsDebug {
 		log.Println("read bytes", count, "error", e)
 	}
 	if n.Cookie != cookie {
 		log.Println("request with unmaching cookie from ", r.RemoteAddr, "agent", r.UserAgent())
+    w.WriteHeader(404)
 		return
 	}
 	if ext != "" {
@@ -175,14 +181,25 @@ func parseURLPath(path string) (vid, fid, ext string) {
 }
 
 func runVolume(cmd *Command, args []string) bool {
+  fileInfo, err := os.Stat(*volumeFolder)
 	//TODO: now default to 1G, this value should come from server?
-	store = storage.NewStore(*vport, *publicUrl, *chunkFolder, *volumes)
+	if err!=nil{
+	  log.Fatalf("No Existing Folder:%s", *volumeFolder)
+	}
+	if !fileInfo.IsDir() {
+    log.Fatalf("Volume Folder should not be a file:%s", *volumeFolder)
+	}
+  perm:=fileInfo.Mode().Perm()
+  log.Println("Volume Folder permission:", perm)
+	
+	store = storage.NewStore(*vport, *publicUrl, *volumeFolder, *maxVolumeCount, *volumes)
 	defer store.Close()
 	http.HandleFunc("/", storeHandler)
 	http.HandleFunc("/status", statusHandler)
 	http.HandleFunc("/admin/assign_volume", assignVolumeHandler)
 	http.HandleFunc("/admin/set_volume_locations_list", setVolumeLocationsHandler)
 
+
 	go func() {
 		for {
 			store.Join(*masterNode)
diff --git a/weed-fs/src/pkg/admin/storage.go b/weed-fs/src/pkg/admin/storage.go
index 8e78b8697..8d9e8a103 100644
--- a/weed-fs/src/pkg/admin/storage.go
+++ b/weed-fs/src/pkg/admin/storage.go
@@ -1,35 +1,10 @@
 package admin
 
 import (
-  "encoding/json"
-  "errors"
-  "strconv"
-  "net/url"
-  "pkg/util"
   "pkg/storage"
   "pkg/topology"
 )
 
-type AllocateVolumeResult struct {
-  Error string
-}
-
-func AllocateVolume(dn *topology.DataNode, vid storage.VolumeId, repType storage.ReplicationType) error{
-  values := make(url.Values)
-  values.Add("volume", vid.String())
-  values.Add("replicationType", repType.String())
-  jsonBlob := util.Post("http://"+dn.Ip+":"+strconv.Itoa(dn.Port)+"/admin/assign_volume", values)
-  var ret AllocateVolumeResult
-  err := json.Unmarshal(jsonBlob, &ret)
-  if err != nil {
-    return err
-  }
-  if ret.Error != "" {
-    return errors.New(ret.Error)
-  }
-  return nil
-}
-
 func SendVolumeLocationsList(t *topology.Topology, vid storage.VolumeId) error{
 //  values := make(url.Values)
 //  values.Add("volumeLocationsList", vid.String())
diff --git a/weed-fs/src/pkg/admin/storage_test.go b/weed-fs/src/pkg/admin/storage_test.go
deleted file mode 100644
index ecc2ab22e..000000000
--- a/weed-fs/src/pkg/admin/storage_test.go
+++ /dev/null
@@ -1,17 +0,0 @@
-package admin
-
-import (
-  "log"
-	"pkg/storage"
-	"pkg/topology"
-	"testing"
-)
-
-func TestXYZ(t *testing.T) {
-	dn := topology.NewDataNode("server1")
-	dn.Ip = "localhost"
-	dn.Port = 8080
-	vid, _:= storage.NewVolumeId("6")
-	out := AllocateVolume(dn,vid,storage.Copy00)
-	log.Println(out)
-}
diff --git a/weed-fs/src/pkg/replication/volume_growth.go b/weed-fs/src/pkg/replication/volume_growth.go
index 3269fcbc6..f6dec8a65 100644
--- a/weed-fs/src/pkg/replication/volume_growth.go
+++ b/weed-fs/src/pkg/replication/volume_growth.go
@@ -1,10 +1,15 @@
 package replication
 
 import (
+	"encoding/json"
+	"errors"
 	"fmt"
 	"math/rand"
+	"net/url"
 	"pkg/storage"
 	"pkg/topology"
+	"pkg/util"
+	"strconv"
 )
 
 /*
@@ -22,17 +27,36 @@ type VolumeGrowth struct {
 	copyAll     int
 }
 
-func (vg *VolumeGrowth) GrowVolumeCopy(copyLevel int, topo *topology.Topology) {
-	switch copyLevel {
-	case 1:
-		for i := 0; i < vg.copy1factor; i++ {
+func NewDefaultVolumeGrowth() *VolumeGrowth {
+	return &VolumeGrowth{copy1factor: 7, copy2factor: 6, copy3factor: 3}
+}
+
+func (vg *VolumeGrowth) GrowByType(repType storage.ReplicationType, topo *topology.Topology) {
+	switch repType {
+	case storage.Copy00:
+		vg.GrowByCountAndType(vg.copy1factor, repType, topo)
+	case storage.Copy10:
+		vg.GrowByCountAndType(vg.copy2factor, repType, topo)
+	case storage.Copy20:
+		vg.GrowByCountAndType(vg.copy3factor, repType, topo)
+	case storage.Copy01:
+		vg.GrowByCountAndType(vg.copy2factor, repType, topo)
+	case storage.Copy11:
+		vg.GrowByCountAndType(vg.copy3factor, repType, topo)
+	}
+
+}
+func (vg *VolumeGrowth) GrowByCountAndType(count int, repType storage.ReplicationType, topo *topology.Topology) {
+	switch repType {
+	case storage.Copy00:
+		for i := 0; i < count; i++ {
 			ret, server, vid := topo.RandomlyReserveOneVolume()
 			if ret {
-				vg.Grow(vid, server)
+				vg.grow(topo, *vid, repType, server)
 			}
 		}
-	case 20:
-		for i := 0; i < vg.copy2factor; i++ {
+	case storage.Copy10:
+		for i := 0; i < count; i++ {
 			nl := topology.NewNodeList(topo.Children(), nil)
 			picked, ret := nl.RandomlyPickN(2)
 			vid := topo.NextVolumeId()
@@ -44,12 +68,12 @@ func (vg *VolumeGrowth) GrowVolumeCopy(copyLevel int, topo *topology.Topology) {
 					}
 				}
 				if len(servers) == 2 {
-					vg.Grow(vid, servers[0], servers[1])
+					vg.grow(topo, vid, repType, servers[0], servers[1])
 				}
 			}
 		}
-	case 30:
-		for i := 0; i < vg.copy3factor; i++ {
+	case storage.Copy20:
+		for i := 0; i < count; i++ {
 			nl := topology.NewNodeList(topo.Children(), nil)
 			picked, ret := nl.RandomlyPickN(3)
 			vid := topo.NextVolumeId()
@@ -61,12 +85,12 @@ func (vg *VolumeGrowth) GrowVolumeCopy(copyLevel int, topo *topology.Topology) {
 					}
 				}
 				if len(servers) == 3 {
-					vg.Grow(vid, servers[0], servers[1], servers[2])
+					vg.grow(topo, vid, repType, servers[0], servers[1], servers[2])
 				}
 			}
 		}
-	case 02:
-		for i := 0; i < vg.copy2factor; i++ {
+	case storage.Copy01:
+		for i := 0; i < count; i++ {
 			//randomly pick one server, and then choose from the same rack
 			ret, server1, vid := topo.RandomlyReserveOneVolume()
 			if ret {
@@ -74,22 +98,53 @@ func (vg *VolumeGrowth) GrowVolumeCopy(copyLevel int, topo *topology.Topology) {
 				exclusion := make(map[string]topology.Node)
 				exclusion[server1.String()] = server1
 				newNodeList := topology.NewNodeList(rack.Children(), exclusion)
-				ret2, server2 := newNodeList.ReserveOneVolume(rand.Intn(newNodeList.FreeSpace()), vid)
-				if ret2 {
-					vg.Grow(vid, server1, server2)
+				if newNodeList.FreeSpace() > 0 {
+					ret2, server2 := newNodeList.ReserveOneVolume(rand.Intn(newNodeList.FreeSpace()), *vid)
+					if ret2 {
+						vg.grow(topo, *vid, repType, server1, server2)
+					}
 				}
 			}
 		}
-	case 12:
-		for i := 0; i < vg.copy3factor; i++ {
+	case storage.Copy11:
+		for i := 0; i < count; i++ {
 		}
 	}
 
 }
-func (vg *VolumeGrowth) Grow(vid storage.VolumeId, servers ...*topology.DataNode) {
+func (vg *VolumeGrowth) grow(topo *topology.Topology, vid storage.VolumeId, repType storage.ReplicationType, servers ...*topology.DataNode) {
 	for _, server := range servers {
-		vi := &storage.VolumeInfo{Id: vid, Size: 0}
-		server.AddVolume(vi)
+		if err := AllocateVolume(server, vid, repType); err == nil {
+			vi := &storage.VolumeInfo{Id: vid, Size: 0}
+			server.AddOrUpdateVolume(vi)
+			topo.RegisterVolumeLayout(vi, server)
+			fmt.Println("added", vid, "to", server)
+		} else {
+			//TODO: need error handling
+			fmt.Println("Failed to assign", vid, "to", servers)
+		}
 	}
 	fmt.Println("Assigning", vid, "to", servers)
 }
+
+type AllocateVolumeResult struct {
+	Error string
+}
+
+func AllocateVolume(dn *topology.DataNode, vid storage.VolumeId, repType storage.ReplicationType) error {
+	values := make(url.Values)
+	values.Add("volume", vid.String())
+	values.Add("replicationType", repType.String())
+	jsonBlob, err := util.Post("http://"+dn.Ip+":"+strconv.Itoa(dn.Port)+"/admin/assign_volume", values)
+	if err != nil {
+		return err
+	}
+	var ret AllocateVolumeResult
+	if err := json.Unmarshal(jsonBlob, &ret); err != nil {
+		return err
+	}
+	if ret.Error != "" {
+		return errors.New(ret.Error)
+	}
+	return nil
+}
diff --git a/weed-fs/src/pkg/replication/volume_growth_test.go b/weed-fs/src/pkg/replication/volume_growth_test.go
index f8e441f03..5068577b1 100644
--- a/weed-fs/src/pkg/replication/volume_growth_test.go
+++ b/weed-fs/src/pkg/replication/volume_growth_test.go
@@ -80,7 +80,7 @@ func setup(topologyLayout string) *topology.Topology {
 	fmt.Println("data:", data)
 
 	//need to connect all nodes first before server adding volumes
-	topo := topology.NewTopology("mynetwork")
+	topo := topology.NewTopology("mynetwork","/tmp","testing",32*1024, 5)
 	mTopology := data.(map[string]interface{})
 	for dcKey, dcValue := range mTopology {
 		dc := topology.NewDataCenter(dcKey)
@@ -97,7 +97,7 @@ func setup(topologyLayout string) *topology.Topology {
 				for _, v := range serverMap["volumes"].([]interface{}) {
 					m := v.(map[string]interface{})
 					vi := &storage.VolumeInfo{Id: storage.VolumeId(int64(m["id"].(float64))), Size: int64(m["size"].(float64))}
-					server.AddVolume(vi)
+					server.AddOrUpdateVolume(vi)
 				}
 				server.UpAdjustMaxVolumeCountDelta(int(serverMap["limit"].(float64)))
 			}
@@ -125,5 +125,15 @@ func TestReserveOneVolume(t *testing.T) {
 	topo := setup(topologyLayout)
   rand.Seed(time.Now().UnixNano())
   vg:=&VolumeGrowth{copy1factor:3,copy2factor:2,copy3factor:1,copyAll:4}
-  vg.GrowVolumeCopy(20,topo)
+  vg.GrowByType(storage.Copy20,topo)
+}
+
+
+func TestXYZ(t *testing.T) {
+  dn := topology.NewDataNode("server1")
+  dn.Ip = "localhost"
+  dn.Port = 8080
+  vid, _:= storage.NewVolumeId("600")
+  out := AllocateVolume(dn,vid,storage.Copy00)
+  fmt.Println(out)
 }
diff --git a/weed-fs/src/pkg/storage/storage_limit.go b/weed-fs/src/pkg/storage/storage_limit.go
deleted file mode 100644
index b40618046..000000000
--- a/weed-fs/src/pkg/storage/storage_limit.go
+++ /dev/null
@@ -1,13 +0,0 @@
-package storage
-
-import (
-)
-
-type StorageLimit struct {
-	sizeLimit     uint64
-}
-
-func NewStorageLimit(desiredLimit uint64) *StorageLimit {
-	sl := &StorageLimit{sizeLimit: desiredLimit}
-	return sl
-}
diff --git a/weed-fs/src/pkg/storage/store.go b/weed-fs/src/pkg/storage/store.go
index 6bc1ec028..a0238d99d 100644
--- a/weed-fs/src/pkg/storage/store.go
+++ b/weed-fs/src/pkg/storage/store.go
@@ -12,19 +12,20 @@ import (
 )
 
 type Store struct {
-	volumes   map[VolumeId]*Volume
-	dir       string
-	Port      int
-	PublicUrl string
-	Limit     StorageLimit
+	volumes        map[VolumeId]*Volume
+	dir            string
+	Port           int
+	PublicUrl      string
+	MaxVolumeCount int
 }
 
-func NewStore(port int, publicUrl, dirname string, volumeListString string) (s *Store) {
-	s = &Store{Port: port, PublicUrl: publicUrl, dir: dirname}
+func NewStore(port int, publicUrl, dirname string, maxVolumeCount int, volumeListString string) (s *Store) {
+	s = &Store{Port: port, PublicUrl: publicUrl, dir: dirname, MaxVolumeCount: maxVolumeCount}
 	s.volumes = make(map[VolumeId]*Volume)
-
 	s.loadExistingVolumes()
-	s.AddVolume(volumeListString, "00")
+	if volumeListString != "" {
+		s.AddVolume(volumeListString, "00")
+	}
 
 	log.Println("Store started on dir:", dirname, "with", len(s.volumes), "volumes", volumeListString)
 	return
@@ -82,16 +83,16 @@ func (s *Store) loadExistingVolumes() {
 		}
 	}
 }
-func (s *Store) Status() *[]*VolumeInfo {
-	stats := new([]*VolumeInfo)
+func (s *Store) Status() []*VolumeInfo {
+	var stats []*VolumeInfo
 	for k, v := range s.volumes {
 		s := new(VolumeInfo)
 		s.Id, s.Size, s.RepType = VolumeId(k), v.Size(), v.replicaType
-		*stats = append(*stats, s)
+		stats = append(stats, s)
 	}
 	return stats
 }
-func (s *Store) Join(mserver string) {
+func (s *Store) Join(mserver string) error {
 	stats := new([]*VolumeInfo)
 	for k, v := range s.volumes {
 		s := new(VolumeInfo)
@@ -103,7 +104,9 @@ func (s *Store) Join(mserver string) {
 	values.Add("port", strconv.Itoa(s.Port))
 	values.Add("publicUrl", s.PublicUrl)
 	values.Add("volumes", string(bytes))
-	util.Post("http://"+mserver+"/dir/join", values)
+	values.Add("maxVolumeCount", strconv.Itoa(s.MaxVolumeCount))
+	_, err := util.Post("http://"+mserver+"/dir/join", values)
+	return err
 }
 func (s *Store) Close() {
 	for _, v := range s.volumes {
@@ -111,22 +114,19 @@ func (s *Store) Close() {
 	}
 }
 func (s *Store) Write(i VolumeId, n *Needle) uint32 {
-	v := s.volumes[i]
-	if v != nil {
+	if v := s.volumes[i]; v != nil {
 		return v.write(n)
 	}
 	return 0
 }
 func (s *Store) Delete(i VolumeId, n *Needle) uint32 {
-	v := s.volumes[i]
-	if v != nil {
+	if v := s.volumes[i]; v != nil {
 		return v.delete(n)
 	}
 	return 0
 }
 func (s *Store) Read(i VolumeId, n *Needle) (int, error) {
-	v := s.volumes[i]
-	if v != nil {
+	if v := s.volumes[i]; v != nil {
 		return v.read(n)
 	}
 	return 0, errors.New("Not Found")
@@ -140,8 +140,7 @@ type VolumeLocations struct {
 func (s *Store) SetVolumeLocations(volumeLocationList []VolumeLocations) error {
 	for _, volumeLocations := range volumeLocationList {
 		vid := volumeLocations.Vid
-		v := s.volumes[vid]
-		if v != nil {
+		if v := s.volumes[vid]; v != nil {
 			v.locations = volumeLocations.Locations
 		}
 	}
diff --git a/weed-fs/src/pkg/storage/volume_info.go b/weed-fs/src/pkg/storage/volume_info.go
index c9ed5265c..01a56a30c 100644
--- a/weed-fs/src/pkg/storage/volume_info.go
+++ b/weed-fs/src/pkg/storage/volume_info.go
@@ -50,8 +50,8 @@ func (r *ReplicationType) String() string {
 	return "00"
 }
 
-func GetReplicationLevelIndex(v *VolumeInfo) int {
-	switch v.RepType {
+func GetReplicationLevelIndex(repType ReplicationType) int {
+	switch repType {
 	case Copy00:
 		return 0
 	case Copy01:
@@ -65,8 +65,8 @@ func GetReplicationLevelIndex(v *VolumeInfo) int {
 	}
 	return -1
 }
-func GetCopyCount(v *VolumeInfo) int {
-	switch v.RepType {
+func GetCopyCount(repType ReplicationType) int {
+	switch repType {
 	case Copy00:
 		return 1
 	case Copy01:
diff --git a/weed-fs/src/pkg/topology/data_center.go b/weed-fs/src/pkg/topology/data_center.go
index 48466e258..5edf7c6eb 100644
--- a/weed-fs/src/pkg/topology/data_center.go
+++ b/weed-fs/src/pkg/topology/data_center.go
@@ -1,6 +1,7 @@
 package topology
 
-import ()
+import (
+)
 
 type DataCenter struct {
 	NodeImpl
@@ -33,3 +34,15 @@ func (dc *DataCenter) GetOrCreateRack(ip string) *Rack {
   dc.LinkChildNode(rack)
   return rack
 }
+
+func (dc *DataCenter) ToMap() interface{}{
+  m := make(map[string]interface{})
+  m["Free"] = dc.FreeSpace()
+  var racks []interface{}
+  for _, c := range dc.Children() {
+    rack := c.(*Rack)
+    racks = append(racks, rack.ToMap())
+  }
+  m["Racks"] = racks
+  return m
+}
diff --git a/weed-fs/src/pkg/topology/data_node.go b/weed-fs/src/pkg/topology/data_node.go
index 254754ccd..1516572fd 100644
--- a/weed-fs/src/pkg/topology/data_node.go
+++ b/weed-fs/src/pkg/topology/data_node.go
@@ -22,22 +22,37 @@ func NewDataNode(id string) *DataNode {
 	return s
 }
 func (dn *DataNode) CreateOneVolume(r int, vid storage.VolumeId) storage.VolumeId {
-	dn.AddVolume(&storage.VolumeInfo{Id: vid})
+	dn.AddOrUpdateVolume(&storage.VolumeInfo{Id: vid})
 	return vid
 }
-func (dn *DataNode) AddVolume(v *storage.VolumeInfo) {
-	dn.volumes[v.Id] = v
-	dn.UpAdjustActiveVolumeCountDelta(1)
-	dn.UpAdjustMaxVolumeId(v.Id)
+func (dn *DataNode) AddOrUpdateVolume(v *storage.VolumeInfo) {
+	if dn.volumes[v.Id] == nil {
+		dn.volumes[v.Id] = v
+		dn.UpAdjustActiveVolumeCountDelta(1)
+		dn.UpAdjustMaxVolumeId(v.Id)
+	}else{
+    dn.volumes[v.Id] = v
+	}
 }
 func (dn *DataNode) GetTopology() *Topology {
-  p := dn.parent
-  for p.Parent()!=nil{
-    p = p.Parent()
-  }
-  t := p.(*Topology)
-  return t
+	p := dn.parent
+	for p.Parent() != nil {
+		p = p.Parent()
+	}
+	t := p.(*Topology)
+	return t
 }
 func (dn *DataNode) MatchLocation(ip string, port int) bool {
-  return dn.Ip == ip && dn.Port == port
+	return dn.Ip == ip && dn.Port == port
+}
+
+func (dn *DataNode) ToMap() interface{} {
+	ret := make(map[string]interface{})
+	ret["Ip"] = dn.Ip
+	ret["Port"] = dn.Port
+	ret["Volumes"] = dn.GetActiveVolumeCount()
+	ret["MaxVolumeCount"] = dn.GetMaxVolumeCount()
+	ret["FreeVolumeCount"] = dn.FreeSpace()
+	ret["PublicUrl"] = dn.PublicUrl
+	return ret
 }
diff --git a/weed-fs/src/pkg/topology/node.go b/weed-fs/src/pkg/topology/node.go
index fb610bd73..cdd9accd4 100644
--- a/weed-fs/src/pkg/topology/node.go
+++ b/weed-fs/src/pkg/topology/node.go
@@ -127,12 +127,10 @@ func (n *NodeImpl) GetMaxVolumeCount() int {
 func (n *NodeImpl) LinkChildNode(node Node) {
 	if n.children[node.Id()] == nil {
 		n.children[node.Id()] = node
-		n.activeVolumeCount += node.GetActiveVolumeCount()
-		n.maxVolumeCount += node.GetMaxVolumeCount()
+		n.UpAdjustMaxVolumeCountDelta(node.GetMaxVolumeCount())
+		n.UpAdjustMaxVolumeId(node.GetMaxVolumeId())
+		n.UpAdjustActiveVolumeCountDelta(node.GetActiveVolumeCount())
 		node.setParent(n)
-		if n.maxVolumeId < node.GetMaxVolumeId() {
-			n.maxVolumeId = node.GetMaxVolumeId()
-		}
 		fmt.Println(n, "adds", node, "volumeCount =", n.activeVolumeCount)
 	}
 }
diff --git a/weed-fs/src/pkg/topology/rack.go b/weed-fs/src/pkg/topology/rack.go
index a52223887..8a09d0bfe 100644
--- a/weed-fs/src/pkg/topology/rack.go
+++ b/weed-fs/src/pkg/topology/rack.go
@@ -24,7 +24,7 @@ func (r *Rack) MatchLocationRange(ip string) bool{
   return r.ipRange.Match(ip)
 }
 
-func (r *Rack) GetOrCreateDataNode(ip string, port int, publicUrl string) *DataNode{
+func (r *Rack) GetOrCreateDataNode(ip string, port int, publicUrl string, maxVolumeCount int) *DataNode{
   for _, c := range r.Children() {
     dn := c.(*DataNode)
     if dn.MatchLocation(ip,port) {
@@ -35,6 +35,19 @@ func (r *Rack) GetOrCreateDataNode(ip string, port int, publicUrl string) *DataN
   dn.Ip = ip
   dn.Port = port
   dn.PublicUrl = publicUrl
+  dn.maxVolumeCount = maxVolumeCount
   r.LinkChildNode(dn)
   return dn
 }
+
+func (rack *Rack) ToMap() interface{}{
+  m := make(map[string]interface{})
+  m["Free"] = rack.FreeSpace()
+  var dns []interface{}
+  for _, c := range rack.Children() {
+    dn := c.(*DataNode)
+    dns = append(dns, dn.ToMap())
+  }
+  m["DataNodes"] = dns
+  return m
+}
diff --git a/weed-fs/src/pkg/topology/topology.go b/weed-fs/src/pkg/topology/topology.go
index 2366c29d0..7a96665af 100644
--- a/weed-fs/src/pkg/topology/topology.go
+++ b/weed-fs/src/pkg/topology/topology.go
@@ -1,8 +1,9 @@
 package topology
 
 import (
-	_ "fmt"
+	"errors"
 	"math/rand"
+	"pkg/directory"
 	"pkg/sequence"
 	"pkg/storage"
 )
@@ -31,10 +32,14 @@ func NewTopology(id string, dirname string, filename string, volumeSizeLimit uin
 	t.sequence = sequence.NewSequencer(dirname, filename)
 	return t
 }
-func (t *Topology) RandomlyReserveOneVolume() (bool, *DataNode, storage.VolumeId) {
+
+func (t *Topology) RandomlyReserveOneVolume() (bool, *DataNode, *storage.VolumeId) {
+  if t.FreeSpace()<=0 {
+    return false, nil, nil
+  }
 	vid := t.NextVolumeId()
 	ret, node := t.ReserveOneVolume(rand.Intn(t.FreeSpace()), vid)
-	return ret, node, vid
+	return ret, node, &vid
 }
 
 func (t *Topology) RandomlyReserveOneVolumeExcept(except []Node) (bool, *DataNode, storage.VolumeId) {
@@ -52,30 +57,68 @@ func (t *Topology) NextVolumeId() storage.VolumeId {
 	return vid.Next()
 }
 
-func (t *Topology) registerVolumeLayout(v *storage.VolumeInfo, dn *DataNode) {
-  replicationTypeIndex := storage.GetReplicationLevelIndex(v)
-  if t.replicaType2VolumeLayout[replicationTypeIndex] == nil {
-    t.replicaType2VolumeLayout[replicationTypeIndex] = NewVolumeLayout(t.volumeSizeLimit, t.pulse)
-  }
-  t.replicaType2VolumeLayout[replicationTypeIndex].RegisterVolume(v, dn)
+func (t *Topology) PickForWrite(repType storage.ReplicationType, count int) (string, int, *DataNode, error) {
+	replicationTypeIndex := storage.GetReplicationLevelIndex(repType)
+	if t.replicaType2VolumeLayout[replicationTypeIndex] == nil {
+		t.replicaType2VolumeLayout[replicationTypeIndex] = NewVolumeLayout(repType, t.volumeSizeLimit, t.pulse)
+	}
+	vid, count, datanodes, err := t.replicaType2VolumeLayout[replicationTypeIndex].PickForWrite(count)
+	if err != nil {
+		return "", 0, nil, errors.New("No writable volumes avalable!")
+	}
+	fileId, count := t.sequence.NextFileId(count)
+	return directory.NewFileId(*vid, fileId, rand.Uint32()).String(), count, datanodes.Head(), nil
+}
+
+func (t *Topology) GetVolumeLayout(repType storage.ReplicationType) *VolumeLayout {
+	replicationTypeIndex := storage.GetReplicationLevelIndex(repType)
+	if t.replicaType2VolumeLayout[replicationTypeIndex] == nil {
+		t.replicaType2VolumeLayout[replicationTypeIndex] = NewVolumeLayout(repType, t.volumeSizeLimit, t.pulse)
+	}
+	return t.replicaType2VolumeLayout[replicationTypeIndex]
 }
 
-func (t *Topology) RegisterVolume(v *storage.VolumeInfo, ip string, port int, publicUrl string) {
+func (t *Topology) RegisterVolumeLayout(v *storage.VolumeInfo, dn *DataNode) {
+	t.GetVolumeLayout(v.RepType).RegisterVolume(v, dn)
+}
+
+func (t *Topology) RegisterVolumes(volumeInfos []storage.VolumeInfo, ip string, port int, publicUrl string, maxVolumeCount int) {
 	dc := t.GetOrCreateDataCenter(ip)
 	rack := dc.GetOrCreateRack(ip)
-	dn := rack.GetOrCreateDataNode(ip, port, publicUrl)
-	dn.AddVolume(v)
-  t.registerVolumeLayout(v,dn)
+	dn := rack.GetOrCreateDataNode(ip, port, publicUrl, maxVolumeCount)
+	for _, v := range volumeInfos {
+		dn.AddOrUpdateVolume(&v)
+		t.RegisterVolumeLayout(&v, dn)
+	}
 }
 
-func (t *Topology) GetOrCreateDataCenter(ip string) *DataCenter{
-  for _, c := range t.Children() {
-    dc := c.(*DataCenter)
-    if dc.MatchLocationRange(ip) {
-      return dc
-    }
-  }
-  dc := NewDataCenter("DefaultDataCenter")
-  t.LinkChildNode(dc)
-  return dc
+func (t *Topology) GetOrCreateDataCenter(ip string) *DataCenter {
+	for _, c := range t.Children() {
+		dc := c.(*DataCenter)
+		if dc.MatchLocationRange(ip) {
+			return dc
+		}
+	}
+	dc := NewDataCenter("DefaultDataCenter")
+	t.LinkChildNode(dc)
+	return dc
+}
+
+func (t *Topology) ToMap() interface{} {
+	m := make(map[string]interface{})
+	m["Free"] = t.FreeSpace()
+	var dcs []interface{}
+	for _, c := range t.Children() {
+		dc := c.(*DataCenter)
+		dcs = append(dcs, dc.ToMap())
+	}
+	m["DataCenters"] = dcs
+	var layouts []interface{}
+	for _, layout := range t.replicaType2VolumeLayout {
+		if layout != nil {
+			layouts = append(layouts, layout.ToMap())
+		}
+	}
+	m["layouts"] = layouts
+	return m
 }
diff --git a/weed-fs/src/pkg/topology/volume_layout.go b/weed-fs/src/pkg/topology/volume_layout.go
index 48d76325e..99859668e 100644
--- a/weed-fs/src/pkg/topology/volume_layout.go
+++ b/weed-fs/src/pkg/topology/volume_layout.go
@@ -8,14 +8,16 @@ import (
 )
 
 type VolumeLayout struct {
+	repType         storage.ReplicationType
 	vid2location    map[storage.VolumeId]*DataNodeLocationList
 	writables       []storage.VolumeId // transient array of writable volume id
 	pulse           int64
 	volumeSizeLimit uint64
 }
 
-func NewVolumeLayout(volumeSizeLimit uint64, pulse int64) *VolumeLayout {
+func NewVolumeLayout(repType storage.ReplicationType, volumeSizeLimit uint64, pulse int64) *VolumeLayout {
 	return &VolumeLayout{
+		repType:         repType,
 		vid2location:    make(map[storage.VolumeId]*DataNodeLocationList),
 		writables:       *new([]storage.VolumeId),
 		pulse:           pulse,
@@ -27,24 +29,37 @@ func (vl *VolumeLayout) RegisterVolume(v *storage.VolumeInfo, dn *DataNode) {
 	if _, ok := vl.vid2location[v.Id]; !ok {
 		vl.vid2location[v.Id] = NewDataNodeLocationList()
 	}
-	vl.vid2location[v.Id].Add(dn)
-	if len(vl.vid2location[v.Id].list) >= storage.GetCopyCount(v) {
-		if uint64(v.Size) < vl.volumeSizeLimit {
-			vl.writables = append(vl.writables, v.Id)
+	if vl.vid2location[v.Id].Add(dn) {
+		if len(vl.vid2location[v.Id].list) == storage.GetCopyCount(v.RepType) {
+			if uint64(v.Size) < vl.volumeSizeLimit {
+				vl.writables = append(vl.writables, v.Id)
+			}
 		}
 	}
 }
 
-func (vl *VolumeLayout) PickForWrite(count int) (int, *DataNodeLocationList, error) {
+func (vl *VolumeLayout) PickForWrite(count int) (*storage.VolumeId, int, *DataNodeLocationList, error) {
 	len_writers := len(vl.writables)
 	if len_writers <= 0 {
 		fmt.Println("No more writable volumes!")
-		return 0, nil, errors.New("No more writable volumes!")
+		return nil, 0, nil, errors.New("No more writable volumes!")
 	}
 	vid := vl.writables[rand.Intn(len_writers)]
 	locationList := vl.vid2location[vid]
 	if locationList != nil {
-		return count, locationList, nil
+		return &vid, count, locationList, nil
 	}
-	return 0, nil, errors.New("Strangely vid " + vid.String() + " is on no machine!")
+	return nil, 0, nil, errors.New("Strangely vid " + vid.String() + " is on no machine!")
+}
+
+func (vl *VolumeLayout) GetActiveVolumeCount() int {
+	return len(vl.writables)
+}
+
+func (vl *VolumeLayout) ToMap() interface{} {
+	m := make(map[string]interface{})
+	m["replication"] = vl.repType.String()
+	m["writables"] = vl.writables
+	//m["locations"] = vl.vid2location
+	return m
 }
diff --git a/weed-fs/src/pkg/topology/volume_location.go b/weed-fs/src/pkg/topology/volume_location.go
index be8218898..92d89ae46 100644
--- a/weed-fs/src/pkg/topology/volume_location.go
+++ b/weed-fs/src/pkg/topology/volume_location.go
@@ -10,13 +10,18 @@ func NewDataNodeLocationList() *DataNodeLocationList {
 	return &DataNodeLocationList{}
 }
 
-func (dnll *DataNodeLocationList) Add(loc *DataNode) {
+func (dnll *DataNodeLocationList) Head() *DataNode {
+	return dnll.list[0]
+}
+
+func (dnll *DataNodeLocationList) Add(loc *DataNode) bool {
 	for _, dnl := range dnll.list {
 		if loc.Ip == dnl.Ip && loc.Port == dnl.Port {
-			break
+			return false
 		}
 	}
 	dnll.list = append(dnll.list, loc)
+	return true
 }
 
 func (dnll *DataNodeLocationList) Refresh(freshThreshHold int64) {
diff --git a/weed-fs/src/pkg/util/post.go b/weed-fs/src/pkg/util/post.go
index 871448785..357b42185 100644
--- a/weed-fs/src/pkg/util/post.go
+++ b/weed-fs/src/pkg/util/post.go
@@ -7,17 +7,17 @@ import (
 	"net/url"
 )
 
-func Post(url string, values url.Values) []byte {
+func Post(url string, values url.Values) ([]byte, error) {
 	r, err := http.PostForm(url, values)
 	if err != nil {
 		log.Println("post:", err)
-		return nil
+		return nil, err
 	}
 	defer r.Body.Close()
 	b, err := ioutil.ReadAll(r.Body)
 	if err != nil {
 		log.Println("post:", err)
-		return nil
+		return nil, err
 	}
-	return b
+	return b, nil
 }