diff --git a/weed-fs/src/cmd/weedc.go b/weed-fs/src/cmd/weedc.go
index 94032a971..00e750e02 100644
--- a/weed-fs/src/cmd/weedc.go
+++ b/weed-fs/src/cmd/weedc.go
@@ -57,7 +57,8 @@ func DeleteHandler(w http.ResponseWriter, r *http.Request) {
 
 func main() {
 	flag.Parse()
-	store = storage.NewStore(*port, *publicServer, *chunkFolder)
+	//TODO: now default to 1G, this value should come from server?
+	store = storage.NewStore(*port, *publicServer, *chunkFolder, 1024*1024*1024, *chunkCount)
 	defer store.Close()
 	http.HandleFunc("/", storeHandler)
 
diff --git a/weed-fs/src/cmd/weeds.go b/weed-fs/src/cmd/weeds.go
index ad423b71e..b888c6c29 100644
--- a/weed-fs/src/cmd/weeds.go
+++ b/weed-fs/src/cmd/weeds.go
@@ -10,17 +10,19 @@ import (
 	"log"
 	"rand"
 	"strconv"
+	"strings"
 )
 
 var (
-	port         = flag.Int("port", 9333, "http listen port")
-	metaFolder  = flag.String("mdir", "/tmp", "data directory to store mappings")
-    mapper *directory.Mapper
+	port       = flag.Int("port", 9333, "http listen port")
+	metaFolder = flag.String("mdir", "/tmp", "data directory to store mappings")
+	capacity   = flag.Int("capacity", 100, "maximum number of volumes to hold")
+	mapper     *directory.Mapper
 )
 
 func dirReadHandler(w http.ResponseWriter, r *http.Request) {
-	volumeId, _ := strconv.Atoui64(r.FormValue("volumeId"))
-	machineList := mapper.Get((uint32)(volumeId))
+	volumeId, _ := strconv.Atoi(r.FormValue("volumeId"))
+	machineList := mapper.Get(volumeId)
 	x := rand.Intn(len(machineList))
 	machine := machineList[x]
 	bytes, _ := json.Marshal(machine)
@@ -37,9 +39,27 @@ func dirReadHandler(w http.ResponseWriter, r *http.Request) {
 }
 func dirWriteHandler(w http.ResponseWriter, r *http.Request) {
 	machineList := mapper.PickForWrite()
-	bytes, _ := json.Marshal(machineList)
-	callback := r.FormValue("callback")
+	writeJson(w, r, machineList)
+}
+func dirJoinHandler(w http.ResponseWriter, r *http.Request) {
+	s := r.RemoteAddr[0:strings.Index(r.RemoteAddr, ":")+1] + r.FormValue("port")
+	publicServer := r.FormValue("publicServer")
+	volumes := new([]storage.VolumeStat)
+	json.Unmarshal([]byte(r.FormValue("volumes")), volumes)
+	capacity, _ := strconv.Atoi(r.FormValue("capacity"))
+	log.Println("Recieved joining request from remote address", s, "capacity=", capacity, "volumes", r.FormValue("volumes"))
+	vids := mapper.Add(*directory.NewMachine(s, publicServer), *volumes, capacity)
+	writeJson(w, r, vids)
+}
+func dirStatusHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain")
+	bytes, _ := json.Marshal(mapper)
+	fmt.Fprint(w, bytes)
+}
+func writeJson(w http.ResponseWriter, r *http.Request, obj interface{}) {
 	w.Header().Set("Content-Type", "application/javascript")
+	bytes, _ := json.Marshal(obj)
+	callback := r.FormValue("callback")
 	if callback == "" {
 		w.Write(bytes)
 	} else {
@@ -48,33 +68,22 @@ func dirWriteHandler(w http.ResponseWriter, r *http.Request) {
 		w.Write(bytes)
 		w.Write([]uint8(")"))
 	}
-}
-func dirJoinHandler(w http.ResponseWriter, r *http.Request) {
-	s := r.FormValue("server")
-	publicServer := r.FormValue("publicServer")
-	volumes := make([]storage.VolumeStat, 0)
-	json.Unmarshal([]byte(r.FormValue("volumes")), volumes)
-	mapper.Add(directory.NewMachine(s, publicServer), volumes)
-}
-func dirStatusHandler(w http.ResponseWriter, r *http.Request) {
-    w.Header().Set("Content-Type", "text/plain")
-    bytes, _ := json.Marshal(mapper)
-    fmt.Fprint(w, bytes)
+	log.Println("JSON Response", string(bytes))
 }
 
 func main() {
 	flag.Parse()
-	mapper = directory.NewMapper(*metaFolder, "directory")
+	mapper = directory.NewMapper(*metaFolder, "directory", *capacity)
 	defer mapper.Save()
 	http.HandleFunc("/dir/read", dirReadHandler)
 	http.HandleFunc("/dir/write", dirWriteHandler)
 	http.HandleFunc("/dir/join", dirJoinHandler)
-    http.HandleFunc("/dir/status", dirStatusHandler)
+	http.HandleFunc("/dir/status", dirStatusHandler)
 
 	log.Println("Start directory service at http://127.0.0.1:" + strconv.Itoa(*port))
 	e := http.ListenAndServe(":"+strconv.Itoa(*port), nil)
-    if e!=nil {
-        log.Fatalf("Fail to start:",e.String())
-    }
+	if e != nil {
+		log.Fatalf("Fail to start:", e.String())
+	}
 
 }
diff --git a/weed-fs/src/pkg/directory/volume_mapping.go b/weed-fs/src/pkg/directory/volume_mapping.go
index 459d7f2b1..ffc90ec7d 100644
--- a/weed-fs/src/pkg/directory/volume_mapping.go
+++ b/weed-fs/src/pkg/directory/volume_mapping.go
@@ -12,12 +12,14 @@ import (
 type Machine struct {
 	Server       string //<server name/ip>[:port]
 	PublicServer string
+	CanWrite     bool
 }
 type Mapper struct {
-    dir              string
-    FileName         string
-    Id2Machine map[uint32][]*Machine
-    LastId uint32
+	dir      string
+	fileName string
+	capacity int
+	Machines [][]Machine //initial version only support one copy per machine
+	writers  [][]Machine // transient value to lookup writers fast
 }
 
 func NewMachine(server, publicServer string) (m *Machine) {
@@ -26,57 +28,88 @@ func NewMachine(server, publicServer string) (m *Machine) {
 	return
 }
 
-func NewMapper(dirname string, filename string) (m *Mapper) {
+func NewMapper(dirname string, filename string, capacity int) (m *Mapper) {
 	m = new(Mapper)
-	m.dir = dirname
-	m.FileName = filename
-	log.Println("Loading virtual to physical:", path.Join(m.dir,m.FileName+".map"))
-	dataFile, e := os.OpenFile(path.Join(m.dir,m.FileName+".map"), os.O_RDONLY, 0644)
-	m.Id2Machine = make(map[uint32][]*Machine)
+	m.dir, m.fileName, m.capacity = dirname, filename, capacity
+	log.Println("Loading volume id to maching mapping:", path.Join(m.dir, m.fileName+".map"))
+	dataFile, e := os.OpenFile(path.Join(m.dir, m.fileName+".map"), os.O_RDONLY, 0644)
+	m.Machines = *new([][]Machine)
+	m.writers = *new([][]Machine)
 	if e != nil {
 		log.Println("Mapping File Read", e)
 	} else {
 		decoder := gob.NewDecoder(dataFile)
-        decoder.Decode(m.LastId)
-		decoder.Decode(m.Id2Machine)
+		decoder.Decode(m.Machines)
+		for _, list := range m.Machines {
+			//TODO: what if a list has mixed readers and writers? Now it's treated as readonly
+			allCanWrite := false
+			for _, entry := range list {
+				allCanWrite = allCanWrite && entry.CanWrite
+			}
+			if allCanWrite {
+				m.writers = append(m.writers, list)
+			}
+		}
 		dataFile.Close()
+        log.Println("Loaded mapping size", len(m.Machines))
 	}
 	return
 }
-func (m *Mapper) PickForWrite() []*Machine {
-	vid := uint32(rand.Intn(len(m.Id2Machine)))
-	return m.Id2Machine[vid]
+func (m *Mapper) PickForWrite() []Machine {
+	vid := rand.Intn(len(m.Machines))
+	return m.Machines[vid]
 }
-func (m *Mapper) Get(vid uint32) []*Machine {
-	return m.Id2Machine[vid]
+func (m *Mapper) Get(vid int) []Machine {
+	return m.Machines[vid]
 }
-func (m *Mapper) Add(machine *Machine, volumes []storage.VolumeStat) {
-    log.Println("Adding store node", machine.Server)
+func (m *Mapper) Add(machine Machine, volumes []storage.VolumeStat, capacity int) []int {
+	log.Println("Adding existing", machine.Server, len(volumes), "volumes to dir", len(m.Machines))
+    log.Println("Adding      new ", machine.Server, capacity - len(volumes), "volumes to dir", len(m.Machines))
+	maxId := len(m.Machines)-1
+	for _, v := range volumes {
+		if maxId < int(v.Id) {
+			maxId = int(v.Id)
+		}
+	}
+	for i := len(m.Machines); i <= maxId; i++ {
+		m.Machines = append(m.Machines, nil)
+	}
+    log.Println("Machine list now is", len(m.Machines))
 	for _, v := range volumes {
-		existing := m.Id2Machine[uint32(v.Id)]
 		found := false
+		existing := m.Machines[v.Id]
 		for _, entry := range existing {
-			if machine == entry {
+			if machine.Server == entry.Server {
 				found = true
 				break
 			}
 		}
 		if !found {
-			m.Id2Machine[uint32(v.Id)] = append(existing, machine)
+			m.Machines[v.Id] = append(existing, machine)
+			log.Println("Setting volume", v.Id, "to", machine.Server)
 		}
-        log.Println(v.Id, "=>", machine.Server)
 	}
+
+    vids := new([]int)
+	for vid,i := len(m.Machines),len(volumes); i < capacity; i,vid=i+1,vid+1 {
+		list := new([]Machine)
+		*list = append(*list, machine)
+		m.Machines = append(m.Machines, *list)
+		log.Println("Adding volume", vid, "from", machine.Server)
+		*vids = append(*vids, vid)
+	}
+
 	m.Save()
+	log.Println("Dir size =>", len(m.Machines))
+	return *vids
 }
 func (m *Mapper) Save() {
-	log.Println("Saving virtual to physical:", path.Join(m.dir,m.FileName+".map"))
-	dataFile, e := os.OpenFile(path.Join(m.dir,m.FileName+".map"), os.O_CREATE|os.O_WRONLY, 0644)
+	log.Println("Saving virtual to physical:", path.Join(m.dir, m.fileName+".map"))
+	dataFile, e := os.OpenFile(path.Join(m.dir, m.fileName+".map"), os.O_CREATE|os.O_WRONLY, 0644)
 	if e != nil {
 		log.Fatalf("Mapping File Save [ERROR] %s\n", e)
 	}
 	defer dataFile.Close()
-	m.Id2Machine = make(map[uint32][]*Machine)
 	encoder := gob.NewEncoder(dataFile)
-    encoder.Encode(m.LastId)
-	encoder.Encode(m.Id2Machine)
+	encoder.Encode(m.Machines)
 }
diff --git a/weed-fs/src/pkg/storage/store.go b/weed-fs/src/pkg/storage/store.go
index 201f50528..e13f47257 100644
--- a/weed-fs/src/pkg/storage/store.go
+++ b/weed-fs/src/pkg/storage/store.go
@@ -11,50 +11,64 @@ import (
 
 type Store struct {
 	volumes      map[uint64]*Volume
+	capacity     int
 	dir          string
-	Port       int
+	Port         int
 	PublicServer string
 }
 type VolumeStat struct {
-	Id     uint64 "id"
-	Status int    "status" //0:read, 1:write
+	Id       uint64 "id"
+	CanWrite bool
 }
 
-func NewStore(port int, publicServer, dirname string) (s *Store) {
+func NewStore(port int, publicServer, dirname string, chunkSize, capacity int) (s *Store) {
 	s = new(Store)
-	s.Port, s.PublicServer, s.dir = port, publicServer, dirname
+	s.Port, s.PublicServer, s.dir, s.capacity = port, publicServer, dirname, capacity
 	s.volumes = make(map[uint64]*Volume)
 
-	counter := uint64(0)
 	files, _ := ioutil.ReadDir(dirname)
 	for _, f := range files {
 		if f.IsDirectory() || !strings.HasSuffix(f.Name, ".dat") {
 			continue
 		}
-		id, err := strconv.Atoui64(f.Name[:-4])
-		if err == nil {
+		id, err := strconv.Atoui64(f.Name[0:(strings.LastIndex(f.Name, ".dat"))])
+		log.Println("Loading data file name:", f.Name)
+		if err != nil {
 			continue
 		}
-		s.volumes[counter] = NewVolume(s.dir, id)
-		counter++
+		s.volumes[id] = NewVolume(s.dir, id)
 	}
-	log.Println("Store started on dir:", dirname, "with", counter, "existing volumes")
+	log.Println("Store started on dir:", dirname, "with", len(s.volumes), "existing volumes")
+	log.Println("Expected capacity=", s.capacity, "volumes")
 	return
 }
 
 func (s *Store) Join(mserver string) {
-	stats := make([]*VolumeStat, len(s.volumes))
+	stats := new([]*VolumeStat)
 	for k, _ := range s.volumes {
 		s := new(VolumeStat)
-		s.Id, s.Status = k, 1
-		stats = append(stats, s)
+		s.Id, s.CanWrite = k, true
+		*stats = append(*stats, s)
 	}
 	bytes, _ := json.Marshal(stats)
 	values := make(url.Values)
 	values.Add("port", strconv.Itoa(s.Port))
-    values.Add("publicServer", s.PublicServer)
+	values.Add("publicServer", s.PublicServer)
 	values.Add("volumes", string(bytes))
-	post("http://"+mserver+"/dir/join", values)
+	log.Println("Registering exiting volumes", string(bytes))
+	values.Add("capacity", strconv.Itoa(s.capacity))
+	retString := post("http://"+mserver+"/dir/join", values)
+	if retString != nil {
+		newVids := new([]int)
+		log.Println("Instructed to create volume",string(retString))
+		e := json.Unmarshal(retString, newVids)
+		if e == nil {
+			for _, vid := range *newVids {
+				s.volumes[uint64(vid)] = NewVolume(s.dir, uint64(vid))
+				log.Println("Adding volume", vid)
+			}
+		}
+	}
 }
 func (s *Store) Close() {
 	for _, v := range s.volumes {
diff --git a/weed-fs/src/pkg/storage/util.go b/weed-fs/src/pkg/storage/util.go
index 3315dbe01..58a415bc0 100644
--- a/weed-fs/src/pkg/storage/util.go
+++ b/weed-fs/src/pkg/storage/util.go
@@ -34,17 +34,17 @@ func uint32toBytes(b []byte, v uint32){
   }
 }
 
-func post(url string, values url.Values)string{
+func post(url string, values url.Values)[]byte{
     r, err := http.PostForm(url, values)
     if err != nil {
         log.Println("post:", err)
-        return ""
+        return nil
     }
     defer r.Body.Close()
     b, err := ioutil.ReadAll(r.Body)
     if err != nil {
         log.Println("post:", err)
-        return ""
+        return nil
     }
-    return string(b)
+    return b
 }
\ No newline at end of file
diff --git a/weed-fs/src/pkg/storage/volume.go b/weed-fs/src/pkg/storage/volume.go
index 6b6db1ba2..3acd2d0e3 100644
--- a/weed-fs/src/pkg/storage/volume.go
+++ b/weed-fs/src/pkg/storage/volume.go
@@ -22,7 +22,6 @@ func NewVolume(dirname string, id uint64) (v *Volume) {
 	v.dir = dirname
 	v.Id = id
 	fileName := strconv.Uitoa64(v.Id)
-	log.Println("file", v.dir, "/", fileName)
 	v.dataFile, e = os.OpenFile(path.Join(v.dir,fileName+".dat"), os.O_RDWR|os.O_CREATE, 0644)
 	if e != nil {
 		log.Fatalf("New Volume [ERROR] %s\n", e)
@@ -39,6 +38,13 @@ func NewVolume(dirname string, id uint64) (v *Volume) {
 
 	return
 }
+func (v *Volume) CanWrite(limit int64) bool {
+    stat, e:=v.dataFile.Stat()
+    if e!=nil{
+       return stat.Size < limit
+    }
+    return false
+}
 func (v *Volume) Close() {
 	close(v.accessChannel)
 	v.dataFile.Close()