diff --git a/weed-fs/src/cmd/weedmaster/weedmaster.go b/weed-fs/src/cmd/weedmaster/weedmaster.go
index 15f46197f..3f6b4daa2 100644
--- a/weed-fs/src/cmd/weedmaster/weedmaster.go
+++ b/weed-fs/src/cmd/weedmaster/weedmaster.go
@@ -37,9 +37,10 @@ func dirLookupHandler(w http.ResponseWriter, r *http.Request) {
 	}
 }
 func dirAssignHandler(w http.ResponseWriter, r *http.Request) {
-	fid, machine, err := mapper.PickForWrite()
+  c:=r.FormValue("count")
+	fid, count, machine, err := mapper.PickForWrite(c)
 	if err == nil {
-		writeJson(w, r, map[string]string{"fid": fid, "url": machine.Url, "publicUrl":machine.PublicUrl})
+		writeJson(w, r, map[string]string{"fid": fid, "url": machine.Url, "publicUrl":machine.PublicUrl, "count":strconv.Itoa(count)})
 	} else {
 		log.Println(err)
 		writeJson(w, r, map[string]string{"error": err.Error()})
diff --git a/weed-fs/src/pkg/directory/volume_mapping.go b/weed-fs/src/pkg/directory/volume_mapping.go
index 267a38a86..947eb65e9 100644
--- a/weed-fs/src/pkg/directory/volume_mapping.go
+++ b/weed-fs/src/pkg/directory/volume_mapping.go
@@ -29,7 +29,8 @@ type Mapper struct {
 	dir      string
 	fileName string
 
-	lock          sync.Mutex
+	volumeLock          sync.Mutex
+  sequenceLock          sync.Mutex
 	Machines      []*Machine
 	vid2machineId map[uint32]int //machineId is +1 of the index of []*Machine, to detect not found entries
 	Writers       []uint32       // transient array of Writers volume id
@@ -65,28 +66,41 @@ func NewMapper(dirname string, filename string, volumeSizeLimit uint64) (m *Mapp
 	}
 	return
 }
-func (m *Mapper) PickForWrite() (string, MachineInfo, error) {
+func (m *Mapper) PickForWrite(c string) (string, int, MachineInfo, error) {
 	len_writers := len(m.Writers)
 	if len_writers <= 0 {
 		log.Println("No more writable volumes!")
-		return "", m.Machines[rand.Intn(len(m.Machines))].Server, errors.New("No more writable volumes!")
+		return "", 0, m.Machines[rand.Intn(len(m.Machines))].Server, errors.New("No more writable volumes!")
 	}
 	vid := m.Writers[rand.Intn(len_writers)]
 	machine_id := m.vid2machineId[vid]
 	if machine_id > 0 {
 		machine := m.Machines[machine_id-1]
-		return NewFileId(vid, m.NextFileId(), rand.Uint32()).String(), machine.Server, nil
+		fileId, count := m.NextFileId(c)
+		if count==0 {
+      return "", 0, m.Machines[rand.Intn(len(m.Machines))].Server, errors.New("Strange count:" + c)
+		}
+		return NewFileId(vid, fileId, rand.Uint32()).String(), count, machine.Server, nil
 	}
-	return "", m.Machines[rand.Intn(len(m.Machines))].Server, errors.New("Strangely vid " + strconv.FormatUint(uint64(vid), 10) + " is on no machine!")
+	return "", 0, m.Machines[rand.Intn(len(m.Machines))].Server, errors.New("Strangely vid " + strconv.FormatUint(uint64(vid), 10) + " is on no machine!")
 }
-func (m *Mapper) NextFileId() uint64 {
-	if m.fileIdCounter <= 0 {
+func (m *Mapper) NextFileId(c string) (uint64,int) {
+  count, parseError := strconv.ParseUint(c,10,64)
+  if parseError!=nil {
+    if len(c)>0{
+      return 0,0
+    }
+    count = 1
+  }
+	if m.fileIdCounter < count {
+	  m.sequenceLock.Lock();
 		m.fileIdCounter = FileIdSaveInterval
 		m.FileIdSequence += FileIdSaveInterval
 		m.saveSequence()
+		m.sequenceLock.Unlock();
 	}
-	m.fileIdCounter--
-	return m.FileIdSequence - m.fileIdCounter
+	m.fileIdCounter = m.fileIdCounter - count
+	return m.FileIdSequence - m.fileIdCounter, int(count)
 }
 func (m *Mapper) Get(vid uint32) (*Machine, error) {
 	machineId := m.vid2machineId[vid]
@@ -98,7 +112,7 @@ func (m *Mapper) Get(vid uint32) (*Machine, error) {
 func (m *Mapper) Add(machine Machine) {
 	//check existing machine, linearly
 	//log.Println("Adding machine", machine.Server.Url)
-	m.lock.Lock()
+	m.volumeLock.Lock()
 	foundExistingMachineId := -1
 	for index, entry := range m.Machines {
 		if machine.Server.Url == entry.Server.Url {
@@ -113,7 +127,7 @@ func (m *Mapper) Add(machine Machine) {
 	} else {
 		m.Machines[machineId] = &machine
 	}
-	m.lock.Unlock()
+	m.volumeLock.Unlock()
 
 	//add to vid2machineId map, and Writers array
 	for _, v := range machine.Volumes {