diff --git a/Makefile b/Makefile
index 0f5bc89d7..52c2ef8ca 100644
--- a/Makefile
+++ b/Makefile
@@ -14,10 +14,10 @@ clean:
 deps:
 	go get $(GO_FLAGS) -d $(SOURCE_DIR)
 
-imports:
-	goimports -w $(SOURCE_DIR)
+fmt:
+	gofmt -w -s ./go/
 
-build: deps imports
+build: deps fmt
 	go build $(GO_FLAGS) -o $(BINARY) $(SOURCE_DIR)
 
 linux: deps
diff --git a/go/glog/glog.go b/go/glog/glog.go
index abd5678d4..6f6c96518 100644
--- a/go/glog/glog.go
+++ b/go/glog/glog.go
@@ -880,7 +880,7 @@ const flushInterval = 30 * time.Second
 
 // flushDaemon periodically flushes the log file buffers.
 func (l *loggingT) flushDaemon() {
-	for _ = range time.NewTicker(flushInterval).C {
+	for range time.NewTicker(flushInterval).C {
 		l.lockAndFlushAll()
 	}
 }
diff --git a/go/operation/lookup.go b/go/operation/lookup.go
index 7719690ec..e929a34bc 100644
--- a/go/operation/lookup.go
+++ b/go/operation/lookup.go
@@ -85,9 +85,9 @@ func LookupFileId(server string, fileId string, readonly bool) (fullUrl string,
 		return "", errors.New("File Not Found")
 	}
 	var u string
-	if readonly{
+	if readonly {
 		u = lookup.Locations.PickForRead().Url
-	}else{
+	} else {
 		u = lookup.Locations.Head().Url
 	}
 	return "http://" + u + "/" + fileId, nil
diff --git a/go/operation/submit.go b/go/operation/submit.go
index 18484680a..8f5239f16 100644
--- a/go/operation/submit.go
+++ b/go/operation/submit.go
@@ -46,7 +46,7 @@ func SubmitFiles(master string, files []FilePart,
 	}
 	ret, err := Assign(master, uint64(len(files)), replication, collection, ttl)
 	if err != nil {
-		for index, _ := range files {
+		for index := range files {
 			results[index].Error = err.Error()
 		}
 		return results, err
diff --git a/go/proto/system_message.proto b/go/proto/system_message.proto
index f89eaf180..31154f8f0 100644
--- a/go/proto/system_message.proto
+++ b/go/proto/system_message.proto
@@ -13,24 +13,6 @@ message VolumeInformationMessage {
     optional uint32 ttl = 10;
 }
 
-enum VolumeTask {
-    Vacuum = 0;
-    Replicate = 1;
-}
-
-enum VolumeTaskStatus {
-    Working = 0;
-    Completed = 1;
-    Failed = 2;
-}
-
-message BusyVolume {
-    required uint32 id = 1;
-    required VolumeTask task = 2;
-    required VolumeTaskStatus status = 3;
-    required int64 start_time = 4;
-}
-
 message JoinMessage {
     optional bool   is_init = 1;
     required string ip = 2;
@@ -42,5 +24,21 @@ message JoinMessage {
     optional string rack = 8;
     repeated VolumeInformationMessage volumes = 9;
     optional uint32 admin_port = 10;
-    repeated BusyVolume busy_volumes = 11;
 }
+
+message CollectionReplicaPlacement {
+    optional string collection = 1;
+    required string replica_placement = 2;
+}
+
+message GlobalSetting {
+    repeated CollectionReplicaPlacement replica_placements = 1;
+    repeated string master_peers = 2;
+}
+
+message JoinResponse {
+    optional GlobalSetting settings = 1;
+}
+
+
+
diff --git a/go/storage/store.go b/go/storage/store.go
index 9b077737d..434c81b0a 100644
--- a/go/storage/store.go
+++ b/go/storage/store.go
@@ -88,6 +88,8 @@ type Store struct {
 	connected       bool
 	volumeSizeLimit uint64 //read from the master
 	masterNodes     *MasterNodes
+	needleMapKind   NeedleMapType
+	TaskManager     *TaskManager
 }
 
 func (s *Store) String() (str string) {
@@ -96,7 +98,13 @@ func (s *Store) String() (str string) {
 }
 
 func NewStore(port int, ip, publicUrl string, dirnames []string, maxVolumeCounts []int, needleMapKind NeedleMapType) (s *Store) {
-	s = &Store{Port: port, Ip: ip, PublicUrl: publicUrl}
+	s = &Store{
+		Port:          port,
+		Ip:            ip,
+		PublicUrl:     publicUrl,
+		TaskManager:   NewTaskManager(),
+		needleMapKind: needleMapKind,
+	}
 	s.Locations = make([]*DiskLocation, 0)
 	for i := 0; i < len(dirnames); i++ {
 		location := &DiskLocation{Directory: dirnames[i], MaxVolumeCount: maxVolumeCounts[i]}
@@ -106,7 +114,7 @@ func NewStore(port int, ip, publicUrl string, dirnames []string, maxVolumeCounts
 	}
 	return
 }
-func (s *Store) AddVolume(volumeListString string, collection string, needleMapKind NeedleMapType, ttlString string) error {
+func (s *Store) AddVolume(volumeListString string, collection string, ttlString string) error {
 	ttl, e := ReadTTL(ttlString)
 	if e != nil {
 		return e
@@ -118,7 +126,7 @@ func (s *Store) AddVolume(volumeListString string, collection string, needleMapK
 			if err != nil {
 				return fmt.Errorf("Volume Id %s is not a valid unsigned integer!", id_string)
 			}
-			e = s.addVolume(VolumeId(id), collection, needleMapKind, ttl)
+			e = s.addVolume(VolumeId(id), collection, ttl)
 		} else {
 			pair := strings.Split(range_string, "-")
 			start, start_err := strconv.ParseUint(pair[0], 10, 64)
@@ -130,7 +138,7 @@ func (s *Store) AddVolume(volumeListString string, collection string, needleMapK
 				return fmt.Errorf("Volume End Id %s is not a valid unsigned integer!", pair[1])
 			}
 			for id := start; id <= end; id++ {
-				if err := s.addVolume(VolumeId(id), collection, needleMapKind, ttl); err != nil {
+				if err := s.addVolume(VolumeId(id), collection, ttl); err != nil {
 					e = err
 				}
 			}
@@ -179,14 +187,14 @@ func (s *Store) findFreeLocation() (ret *DiskLocation) {
 	}
 	return ret
 }
-func (s *Store) addVolume(vid VolumeId, collection string, needleMapKind NeedleMapType, ttl *TTL) error {
+func (s *Store) addVolume(vid VolumeId, collection string, ttl *TTL) error {
 	if s.findVolume(vid) != nil {
 		return fmt.Errorf("Volume Id %d already exists!", vid)
 	}
 	if location := s.findFreeLocation(); location != nil {
 		glog.V(0).Infof("In dir %s adds volume:%v collection:%s ttl:%v",
-			location.Directory, vid, collection,  ttl)
-		if volume, err := NewVolume(location.Directory, collection, vid, needleMapKind, ttl); err == nil {
+			location.Directory, vid, collection, ttl)
+		if volume, err := NewVolume(location.Directory, collection, vid, s.needleMapKind, ttl); err == nil {
 			location.volumes[vid] = volume
 			return nil
 		} else {
@@ -384,7 +392,7 @@ func (s *Store) HasVolume(i VolumeId) bool {
 
 type VolumeWalker func(v *Volume) (e error)
 
-func (s *Store) WalkVolume(walker VolumeWalker) error{
+func (s *Store) WalkVolume(walker VolumeWalker) error {
 	for _, location := range s.Locations {
 		for _, v := range location.volumes {
 			if e := walker(v); e != nil {
diff --git a/go/storage/store_task.go b/go/storage/store_task.go
new file mode 100644
index 000000000..2f8c0515f
--- /dev/null
+++ b/go/storage/store_task.go
@@ -0,0 +1,133 @@
+package storage
+
+import (
+	"errors"
+	"net/url"
+	"time"
+)
+
+const (
+	TaskVacuum  = "VACUUM"
+	TaskReplica = "REPLICA"
+	TaskBalance = "BALANCE"
+)
+
+var (
+	ErrTaskNotFinish = errors.New("TaskNotFinish")
+	ErrTaskNotFound  = errors.New("TaskNotFound")
+	ErrTaskInvalid   = errors.New("TaskInvalid")
+	ErrTaskExists    = errors.New("TaskExists")
+)
+
+type TaskWorker interface {
+	Run() error
+	Commit() error
+	Clean() error
+	Info() url.Values
+}
+
+type Task struct {
+	startTime time.Time
+	worker    TaskWorker
+	ch        chan bool
+	result    error
+}
+
+type TaskManager struct {
+	TaskList map[string]*Task
+}
+
+func NewTask(worker TaskWorker) *Task {
+	t := &Task{
+		worker:    worker,
+		startTime: time.Now(),
+		result:    ErrTaskNotFinish,
+		ch:        make(chan bool, 1),
+	}
+	go func(t *Task) {
+		t.result = t.worker.Run()
+		t.ch <- true
+	}(t)
+	return t
+}
+
+func (t *Task) QueryResult(waitDuration time.Duration) error {
+	if t.result == ErrTaskNotFinish && waitDuration > 0 {
+		select {
+		case <-time.After(waitDuration):
+		case <-t.ch:
+		}
+	}
+	return t.result
+}
+
+func NewTaskManager() *TaskManager {
+	return &TaskManager{
+		TaskList: make(map[string]*Task),
+	}
+}
+
+func (tm *TaskManager) NewTask(s *Store, args url.Values) (tid string, e error) {
+	tt := args.Get("task")
+	vid := args.Get("volumme")
+	tid = tt + "-" + vid
+	if _, ok := tm.TaskList[tid]; ok {
+		return tid, ErrTaskExists
+	}
+	var tw TaskWorker
+	switch tt {
+	case TaskVacuum:
+		tw, e = NewVacuumTask(s, args)
+	case TaskReplica:
+		tw, e = NewReplicaTask(s, args)
+	case TaskBalance:
+	}
+	if e != nil {
+		return
+	}
+	if tw == nil {
+		return "", ErrTaskInvalid
+	}
+	tm.TaskList[tid] = NewTask(tw)
+	return tid, nil
+}
+
+func (tm *TaskManager) QueryResult(tid string, waitDuration time.Duration) (e error) {
+	t, ok := tm.TaskList[tid]
+	if !ok {
+		return ErrTaskNotFound
+	}
+	return t.QueryResult(waitDuration)
+}
+
+func (tm *TaskManager) Commit(tid string) (e error) {
+	t, ok := tm.TaskList[tid]
+	if !ok {
+		return ErrTaskNotFound
+	}
+	if t.QueryResult(time.Second*30) == ErrTaskNotFinish {
+		return ErrTaskNotFinish
+	}
+	delete(tm.TaskList, tid)
+	return t.worker.Commit()
+}
+
+func (tm *TaskManager) Clean(tid string) (e error) {
+	t, ok := tm.TaskList[tid]
+	if !ok {
+		return ErrTaskNotFound
+	}
+	if t.QueryResult(time.Second*30) == ErrTaskNotFinish {
+		return ErrTaskNotFinish
+	}
+	delete(tm.TaskList, tid)
+	return t.worker.Clean()
+}
+
+func (tm *TaskManager) ElapsedDuration(tid string) (time.Duration, error) {
+	t, ok := tm.TaskList[tid]
+	if !ok {
+		return 0, ErrTaskNotFound
+	}
+	return time.Since(t.startTime), nil
+}
diff --git a/go/storage/store_task_replication.go b/go/storage/store_task_replication.go
new file mode 100644
index 000000000..6cad71ac4
--- /dev/null
+++ b/go/storage/store_task_replication.go
@@ -0,0 +1,114 @@
+package storage
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+	"os"
+	"path"
+
+	"github.com/chrislusf/seaweedfs/go/util"
+)
+
+type ReplicaTask struct {
+	VID         VolumeId
+	Collection  string
+	SrcDataNode string
+	s           *Store
+	location    *DiskLocation
+}
+
+func NewReplicaTask(s *Store, args url.Values) (*ReplicaTask, error) {
+	volumeIdString := args.Get("volume")
+	vid, err := NewVolumeId(volumeIdString)
+	if err != nil {
+		return nil, fmt.Errorf("Volume Id %s is not a valid unsigned integer", volumeIdString)
+	}
+	source := args.Get("source")
+	if source == "" {
+		return nil, errors.New("Invalid source data node.")
+
+	}
+	location := s.findFreeLocation()
+	if location == nil {
+		return nil, errors.New("No more free space left")
+	}
+	collection := args.Get("collection")
+	return &ReplicaTask{
+		VID:         vid,
+		Collection:  collection,
+		SrcDataNode: source,
+		s:           s,
+		location:    location,
+	}, nil
+}
+
+func (t *ReplicaTask) Run() error {
+	ch := make(chan error)
+	go func() {
+		idxUrl := util.MkUrl(t.SrcDataNode, "/admin/sync/index", url.Values{"volume": {t.VID.String()}})
+		e := util.DownloadToFile(idxUrl, t.FileName()+".repx")
+		if e != nil {
+			e = fmt.Errorf("Replicat error: %s, %v", idxUrl, e)
+		}
+		ch <- e
+	}()
+	go func() {
+		datUrl := util.MkUrl(t.SrcDataNode, "/admin/sync/vol_data", url.Values{"volume": {t.VID.String()}})
+		e := util.DownloadToFile(datUrl, t.FileName()+".repd")
+		if e != nil {
+			e = fmt.Errorf("Replicat error: %s, %v", datUrl, e)
+		}
+		ch <- e
+	}()
+	errs := make([]error, 0, 2)
+	for i := 0; i < 2; i++ {
+		if e := <-ch; e != nil {
+			errs = append(errs, e)
+		}
+	}
+	if len(errs) == 0 {
+		return nil
+	} else {
+		return fmt.Errorf("%v", errs)
+	}
+}
+
+func (t *ReplicaTask) Commit() error {
+	var (
+		volume *Volume
+		e      error
+	)
+
+	if e = os.Rename(t.FileName()+".repd", t.FileName()+".dat"); e != nil {
+		return e
+	}
+	if e = os.Rename(t.FileName()+".repx", t.FileName()+".idx"); e != nil {
+		return e
+	}
+	volume, e = NewVolume(t.location.Directory, t.Collection, t.VID, t.s.needleMapKind, nil)
+	if e == nil {
+		t.location.volumes[t.VID] = volume
+	}
+	return e
+}
+
+func (t *ReplicaTask) Clean() error {
+	os.Remove(t.FileName() + ".repx")
+	os.Remove(t.FileName() + ".repd")
+	return nil
+}
+
+func (t *ReplicaTask) Info() url.Values {
+	//TODO
+	return url.Values{}
+}
+
+func (t *ReplicaTask) FileName() (fileName string) {
+	if t.Collection == "" {
+		fileName = path.Join(t.location.Directory, t.VID.String())
+	} else {
+		fileName = path.Join(t.location.Directory, t.Collection+"_"+t.VID.String())
+	}
+	return
+}
diff --git a/go/storage/store_task_vacuum.go b/go/storage/store_task_vacuum.go
new file mode 100644
index 000000000..1da789960
--- /dev/null
+++ b/go/storage/store_task_vacuum.go
@@ -0,0 +1,40 @@
+package storage
+
+import (
+	"fmt"
+	"net/url"
+)
+
+type VacuumTask struct {
+	V *Volume
+}
+
+func NewVacuumTask(s *Store, args url.Values) (*VacuumTask, error) {
+	volumeIdString := args.Get("volumme")
+	vid, err := NewVolumeId(volumeIdString)
+	if err != nil {
+		return nil, fmt.Errorf("Volume Id %s is not a valid unsigned integer", volumeIdString)
+	}
+	v := s.findVolume(vid)
+	if v == nil {
+		return nil, fmt.Errorf("volume id %d is not found", vid)
+	}
+	return &VacuumTask{V: v}, nil
+}
+
+func (t *VacuumTask) Run() error {
+	return t.V.Compact()
+}
+
+func (t *VacuumTask) Commit() error {
+	return t.V.commitCompact()
+}
+
+func (t *VacuumTask) Clean() error {
+	return t.V.cleanCompact()
+}
+
+func (t *VacuumTask) Info() url.Values {
+	//TODO
+	return url.Values{}
+}
diff --git a/go/storage/volume_info_test.go b/go/storage/volume_info_test.go
index 9a9c43ad2..c90ca2336 100644
--- a/go/storage/volume_info_test.go
+++ b/go/storage/volume_info_test.go
@@ -4,13 +4,13 @@ import "testing"
 
 func TestSortVolumeInfos(t *testing.T) {
 	vis := []*VolumeInfo{
-		&VolumeInfo{
+		{
 			Id: 2,
 		},
-		&VolumeInfo{
+		{
 			Id: 1,
 		},
-		&VolumeInfo{
+		{
 			Id: 3,
 		},
 	}
diff --git a/go/storage/volume_replicate.go b/go/storage/volume_pure_reader.go
similarity index 87%
rename from go/storage/volume_replicate.go
rename to go/storage/volume_pure_reader.go
index 00b9cd14e..a03c88327 100644
--- a/go/storage/volume_replicate.go
+++ b/go/storage/volume_pure_reader.go
@@ -27,7 +27,7 @@ func (s DirtyDatas) Search(offset int64) int {
 	})
 }
 
-type CleanReader struct {
+type PureReader struct {
 	Dirtys   DirtyDatas
 	DataFile *os.File
 	pr       *io.PipeReader
@@ -62,7 +62,7 @@ func ScanDirtyData(indexFileContent []byte) (dirtys DirtyDatas) {
 	return dirtys
 }
 
-func (cr *CleanReader) Seek(offset int64, whence int) (int64, error) {
+func (cr *PureReader) Seek(offset int64, whence int) (int64, error) {
 	oldOff, e := cr.DataFile.Seek(0, 1)
 	if e != nil {
 		return 0, e
@@ -77,7 +77,7 @@ func (cr *CleanReader) Seek(offset int64, whence int) (int64, error) {
 	return newOff, nil
 }
 
-func (cr *CleanReader) Size() (int64, error) {
+func (cr *PureReader) Size() (int64, error) {
 	fi, e := cr.DataFile.Stat()
 	if e != nil {
 		return 0, e
@@ -85,7 +85,7 @@ func (cr *CleanReader) Size() (int64, error) {
 	return fi.Size(), nil
 }
 
-func (cdr *CleanReader) WriteTo(w io.Writer) (written int64, err error) {
+func (cdr *PureReader) WriteTo(w io.Writer) (written int64, err error) {
 	off, e := cdr.DataFile.Seek(0, 1)
 	if e != nil {
 		return 0, nil
@@ -143,21 +143,21 @@ func (cdr *CleanReader) WriteTo(w io.Writer) (written int64, err error) {
 	return
 }
 
-func (cr *CleanReader) ReadAt(p []byte, off int64) (n int, err error) {
+func (cr *PureReader) ReadAt(p []byte, off int64) (n int, err error) {
 	cr.Seek(off, 0)
 	return cr.Read(p)
 }
 
-func (cr *CleanReader) Read(p []byte) (int, error) {
+func (cr *PureReader) Read(p []byte) (int, error) {
 	return cr.getPipeReader().Read(p)
 }
 
-func (cr *CleanReader) Close() (e error) {
+func (cr *PureReader) Close() (e error) {
 	cr.closePipe(true)
 	return cr.DataFile.Close()
 }
 
-func (cr *CleanReader) closePipe(lock bool) (e error) {
+func (cr *PureReader) closePipe(lock bool) (e error) {
 	if lock {
 		cr.mutex.Lock()
 		defer cr.mutex.Unlock()
@@ -177,7 +177,7 @@ func (cr *CleanReader) closePipe(lock bool) (e error) {
 	return e
 }
 
-func (cr *CleanReader) getPipeReader() io.Reader {
+func (cr *PureReader) getPipeReader() io.Reader {
 	cr.mutex.Lock()
 	defer cr.mutex.Unlock()
 	if cr.pr != nil && cr.pw != nil {
@@ -192,7 +192,7 @@ func (cr *CleanReader) getPipeReader() io.Reader {
 	return cr.pr
 }
 
-func (v *Volume) GetVolumeCleanReader() (cr *CleanReader, err error) {
+func (v *Volume) GetVolumeCleanReader() (cr *PureReader, err error) {
 	var dirtys DirtyDatas
 	if indexData, e := v.nm.IndexFileContent(); e != nil {
 		return nil, err
@@ -204,7 +204,7 @@ func (v *Volume) GetVolumeCleanReader() (cr *CleanReader, err error) {
 	if e != nil {
 		return nil, e
 	}
-	cr = &CleanReader{
+	cr = &PureReader{
 		Dirtys:   dirtys,
 		DataFile: dataFile,
 	}
diff --git a/go/storage/volume_super_block.go b/go/storage/volume_super_block.go
index 5c7d01c21..fc8c33900 100644
--- a/go/storage/volume_super_block.go
+++ b/go/storage/volume_super_block.go
@@ -21,9 +21,9 @@ const (
 * Rest bytes: Reserved
  */
 type SuperBlock struct {
-	version          Version
-	Ttl              *TTL
-	CompactRevision  uint16
+	version         Version
+	Ttl             *TTL
+	CompactRevision uint16
 }
 
 func (s *SuperBlock) Version() Version {
diff --git a/go/storage/volume_vacuum.go b/go/storage/volume_vacuum.go
index a2b7cdf76..3941a568f 100644
--- a/go/storage/volume_vacuum.go
+++ b/go/storage/volume_vacuum.go
@@ -46,6 +46,12 @@ func (v *Volume) commitCompact() error {
 	return nil
 }
 
+func (v *Volume) cleanCompact() error {
+	os.Remove(v.FileName() + ".cpd")
+	os.Remove(v.FileName() + ".cpx")
+	return nil
+}
+
 func (v *Volume) copyDataAndGenerateIndexFile(dstName, idxName string) (err error) {
 	var (
 		dst, idx *os.File
diff --git a/go/topology/data_node.go b/go/topology/data_node.go
index 72ced1b73..19f3870de 100644
--- a/go/topology/data_node.go
+++ b/go/topology/data_node.go
@@ -31,7 +31,7 @@ func (dn *DataNode) String() string {
 	return fmt.Sprintf("Node:%s, volumes:%v, Ip:%s, Port:%d, PublicUrl:%s, Dead:%v", dn.NodeImpl.String(), dn.volumes, dn.Ip, dn.Port, dn.PublicUrl, dn.Dead)
 }
 
-func (dn *DataNode) AddOrUpdateVolume(v storage.VolumeInfo){
+func (dn *DataNode) AddOrUpdateVolume(v storage.VolumeInfo) {
 	if _, ok := dn.volumes[v.Id]; !ok {
 		dn.volumes[v.Id] = v
 		dn.UpAdjustVolumeCountDelta(1)
diff --git a/go/topology/topology_event_handling.go b/go/topology/topology_event_handling.go
index 6dfa07487..2bb2a9d66 100644
--- a/go/topology/topology_event_handling.go
+++ b/go/topology/topology_event_handling.go
@@ -21,7 +21,7 @@ func (t *Topology) StartRefreshWritableVolumes(garbageThreshold string) {
 	go func(garbageThreshold string) {
 		c := time.Tick(15 * time.Minute)
 		if t.IsLeader() {
-			for _ = range c {
+			for range c {
 				t.Vacuum(garbageThreshold)
 			}
 		}
diff --git a/go/topology/topology_replicate.go b/go/topology/topology_replicate.go
new file mode 100644
index 000000000..8c9281390
--- /dev/null
+++ b/go/topology/topology_replicate.go
@@ -0,0 +1,25 @@
+package topology
+
+import "github.com/chrislusf/seaweedfs/go/glog"
+
+func (t *Topology) Replicate(garbageThreshold string) int {
+	glog.V(0).Infoln("Start replicate on demand")
+	for _, col := range t.collectionMap.Items {
+		c := col.(*Collection)
+		glog.V(0).Infoln("replicate on collection:", c.Name)
+		for _, vl := range c.storageType2VolumeLayout.Items {
+			if vl != nil {
+				volumeLayout := vl.(*VolumeLayout)
+				copyCount := volumeLayout.rp.GetCopyCount()
+				for vid, locationList := range volumeLayout.vid2location {
+					if locationList.Length() < copyCount {
+						//set volume readonly
+						glog.V(0).Infoln("replicate volume :", vid)
+
+					}
+				}
+			}
+		}
+	}
+	return 0
+}
diff --git a/go/topology/topology_vacuum.go b/go/topology/topology_vacuum.go
index 48bc8311d..cba3e8a16 100644
--- a/go/topology/topology_vacuum.go
+++ b/go/topology/topology_vacuum.go
@@ -26,7 +26,7 @@ func batchVacuumVolumeCheck(vl *VolumeLayout, vid storage.VolumeId, locationlist
 		}(index, dn.Url(), vid)
 	}
 	isCheckSuccess := true
-	for _ = range locationlist.list {
+	for range locationlist.list {
 		select {
 		case canVacuum := <-ch:
 			isCheckSuccess = isCheckSuccess && canVacuum
@@ -53,7 +53,7 @@ func batchVacuumVolumeCompact(vl *VolumeLayout, vid storage.VolumeId, locationli
 		}(index, dn.Url(), vid)
 	}
 	isVacuumSuccess := true
-	for _ = range locationlist.list {
+	for range locationlist.list {
 		select {
 		case _ = <-ch:
 		case <-time.After(30 * time.Minute):
diff --git a/go/topology/volume_growth.go b/go/topology/volume_growth.go
index 3de1a771f..31307ffe0 100644
--- a/go/topology/volume_growth.go
+++ b/go/topology/volume_growth.go
@@ -192,11 +192,11 @@ func (vg *VolumeGrowth) grow(topo *Topology, vid storage.VolumeId, option *Volum
 	for _, server := range servers {
 		if err := AllocateVolume(server, vid, option); err == nil {
 			vi := storage.VolumeInfo{
-				Id:               vid,
-				Size:             0,
-				Collection:       option.Collection,
-				Ttl:              option.Ttl,
-				Version:          storage.CurrentVersion,
+				Id:         vid,
+				Size:       0,
+				Collection: option.Collection,
+				Ttl:        option.Ttl,
+				Version:    storage.CurrentVersion,
 			}
 			server.AddOrUpdateVolume(vi)
 			topo.RegisterVolumeLayout(vi, server)
diff --git a/go/topology/volume_layout.go b/go/topology/volume_layout.go
index 050f576ce..8a922f945 100644
--- a/go/topology/volume_layout.go
+++ b/go/topology/volume_layout.go
@@ -25,7 +25,6 @@ func NewVolumeLayout(rp *storage.ReplicaPlacement, ttl *storage.TTL, volumeSizeL
 		rp:              rp,
 		ttl:             ttl,
 		vid2location:    make(map[storage.VolumeId]*VolumeLocationList),
-		writables:       *new([]storage.VolumeId),
 		volumeSizeLimit: volumeSizeLimit,
 	}
 }
@@ -43,7 +42,7 @@ func (vl *VolumeLayout) RegisterVolume(v *storage.VolumeInfo, dn *DataNode) {
 	}
 	vl.vid2location[v.Id].Set(dn)
 	glog.V(4).Infoln("volume", v.Id, "added to dn", dn.Id(), "len", vl.vid2location[v.Id].Length())
-	//TODO
+	//TODO balancing data when have more replications
 	if vl.vid2location[v.Id].Length() == vl.rp.GetCopyCount() && vl.isWritable(v) {
 		vl.AddToWritable(v.Id)
 	} else {
diff --git a/go/util/http_util.go b/go/util/http_util.go
index 29b2043ee..5060c77ad 100644
--- a/go/util/http_util.go
+++ b/go/util/http_util.go
@@ -11,6 +11,8 @@ import (
 	"net/url"
 	"strings"
 
+	"os"
+
 	"github.com/chrislusf/seaweedfs/go/security"
 )
 
@@ -140,6 +142,10 @@ func DownloadUrl(fileUrl string) (filename string, rc io.ReadCloser, e error) {
 	if err != nil {
 		return "", nil, err
 	}
+	if response.StatusCode != http.StatusOK {
+		response.Body.Close()
+		return "", nil, fmt.Errorf("%s: %s", fileUrl, response.Status)
+	}
 	contentDisposition := response.Header["Content-Disposition"]
 	if len(contentDisposition) > 0 {
 		if strings.HasPrefix(contentDisposition[0], "filename=") {
@@ -151,6 +157,21 @@ func DownloadUrl(fileUrl string) (filename string, rc io.ReadCloser, e error) {
 	return
 }
 
+func DownloadToFile(fileUrl, savePath string) (e error) {
+	_, rc, err := DownloadUrl(fileUrl)
+	if err != nil {
+		return err
+	}
+	defer rc.Close()
+	var f *os.File
+	if f, e = os.OpenFile(savePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.ModePerm); e != nil {
+		return
+	}
+	_, e = io.Copy(f, rc)
+	f.Close()
+	return
+}
+
 func Do(req *http.Request) (resp *http.Response, err error) {
 	return client.Do(req)
 }
diff --git a/go/util/url_util.go b/go/util/url_util.go
new file mode 100644
index 000000000..7204d08b0
--- /dev/null
+++ b/go/util/url_util.go
@@ -0,0 +1,13 @@
+package util
+
+import "net/url"
+
+func MkUrl(host, path string, args url.Values) string {
+	u := url.URL{
+		Scheme: "http",
+		Host:   host,
+		Path:   path,
+	}
+	u.RawQuery = args.Encode()
+	return u.String()
+}
diff --git a/go/weed/shell.go b/go/weed/shell.go
index 144621b09..feac5ddd4 100644
--- a/go/weed/shell.go
+++ b/go/weed/shell.go
@@ -20,8 +20,6 @@ var cmdShell = &Command{
   `,
 }
 
-var ()
-
 func runShell(command *Command, args []string) bool {
 	r := bufio.NewReader(os.Stdin)
 	o := bufio.NewWriter(os.Stdout)
diff --git a/go/weed/signal_handling.go b/go/weed/signal_handling.go
index 2004bb088..9c3908ce3 100644
--- a/go/weed/signal_handling.go
+++ b/go/weed/signal_handling.go
@@ -22,7 +22,7 @@ func OnInterrupt(fn func()) {
 		syscall.SIGTERM,
 		syscall.SIGQUIT)
 	go func() {
-		for _ = range signalChan {
+		for range signalChan {
 			fn()
 			os.Exit(0)
 		}
diff --git a/go/weed/weed_server/common.go b/go/weed/weed_server/common.go
index a7fa2de53..89499af40 100644
--- a/go/weed/weed_server/common.go
+++ b/go/weed/weed_server/common.go
@@ -69,7 +69,12 @@ func writeJsonQuiet(w http.ResponseWriter, r *http.Request, httpStatus int, obj
 }
 func writeJsonError(w http.ResponseWriter, r *http.Request, httpStatus int, err error) {
 	m := make(map[string]interface{})
-	m["error"] = err.Error()
+	if err == nil {
+		m["error"] = ""
+	} else {
+		m["error"] = err.Error()
+
+	}
 	writeJsonQuiet(w, r, httpStatus, m)
 }
 
diff --git a/go/weed/weed_server/volume_server.go b/go/weed/weed_server/volume_server.go
index c1f5acb5a..fbf0339e3 100644
--- a/go/weed/weed_server/volume_server.go
+++ b/go/weed/weed_server/volume_server.go
@@ -20,7 +20,6 @@ type VolumeServer struct {
 	store        *storage.Store
 	guard        *security.Guard
 
-	needleMapKind     storage.NeedleMapType
 	FixJpgOrientation bool
 	ReadRedirect      bool
 }
@@ -38,12 +37,11 @@ func NewVolumeServer(adminMux, publicMux *http.ServeMux, ip string,
 		pulseSeconds:      pulseSeconds,
 		dataCenter:        dataCenter,
 		rack:              rack,
-		needleMapKind:     needleMapKind,
 		FixJpgOrientation: fixJpgOrientation,
 		ReadRedirect:      readRedirect,
 	}
 	vs.SetMasterNode(masterNode)
-	vs.store = storage.NewStore(port, ip, publicUrl, folders, maxCounts, vs.needleMapKind)
+	vs.store = storage.NewStore(port, ip, publicUrl, folders, maxCounts, needleMapKind)
 
 	vs.guard = security.NewGuard(whiteList, "")
 
@@ -59,6 +57,11 @@ func NewVolumeServer(adminMux, publicMux *http.ServeMux, ip string,
 	adminMux.HandleFunc("/admin/sync/index", vs.guard.WhiteList(vs.getVolumeIndexContentHandler))
 	adminMux.HandleFunc("/admin/sync/data", vs.guard.WhiteList(vs.getVolumeDataContentHandler))
 	adminMux.HandleFunc("/admin/sync/vol_data", vs.guard.WhiteList(vs.getVolumeCleanDataHandler))
+	adminMux.HandleFunc("/admin/task/new", vs.guard.WhiteList(vs.newTaskHandler))
+	adminMux.HandleFunc("/admin/task/query", vs.guard.WhiteList(vs.queryTaskHandler))
+	adminMux.HandleFunc("/admin/task/commit", vs.guard.WhiteList(vs.commitTaskHandler))
+	adminMux.HandleFunc("/admin/task/clean", vs.guard.WhiteList(vs.cleanTaskHandler))
+	adminMux.HandleFunc("/admin/task/all", vs.guard.WhiteList(vs.allTaskHandler))
 	adminMux.HandleFunc("/stats/counter", vs.guard.WhiteList(statsCounterHandler))
 	adminMux.HandleFunc("/stats/memory", vs.guard.WhiteList(statsMemoryHandler))
 	adminMux.HandleFunc("/stats/disk", vs.guard.WhiteList(vs.statsDiskHandler))
diff --git a/go/weed/weed_server/volume_server_handlers_admin.go b/go/weed/weed_server/volume_server_handlers_admin.go
index 9a304d895..779d6f99d 100644
--- a/go/weed/weed_server/volume_server_handlers_admin.go
+++ b/go/weed/weed_server/volume_server_handlers_admin.go
@@ -26,7 +26,7 @@ func (vs *VolumeServer) statusHandler(w http.ResponseWriter, r *http.Request) {
 }
 
 func (vs *VolumeServer) assignVolumeHandler(w http.ResponseWriter, r *http.Request) {
-	err := vs.store.AddVolume(r.FormValue("volume"), r.FormValue("collection"), vs.needleMapKind, r.FormValue("ttl"))
+	err := vs.store.AddVolume(r.FormValue("volume"), r.FormValue("collection"), r.FormValue("ttl"))
 	if err == nil {
 		writeJsonQuiet(w, r, http.StatusAccepted, map[string]string{"error": ""})
 	} else {
diff --git a/go/weed/weed_server/volume_server_handlers_task.go b/go/weed/weed_server/volume_server_handlers_task.go
new file mode 100644
index 000000000..cd0319660
--- /dev/null
+++ b/go/weed/weed_server/volume_server_handlers_task.go
@@ -0,0 +1,63 @@
+package weed_server
+
+import (
+	"net/http"
+
+	"time"
+
+	"strings"
+
+	"github.com/chrislusf/seaweedfs/go/glog"
+	"github.com/chrislusf/seaweedfs/go/storage"
+)
+
+func (vs *VolumeServer) newTaskHandler(w http.ResponseWriter, r *http.Request) {
+	tid, e := vs.store.TaskManager.NewTask(vs.store, r.Form)
+	if e == nil {
+		writeJsonQuiet(w, r, http.StatusOK, map[string]string{"tid": tid})
+	} else {
+		writeJsonError(w, r, http.StatusInternalServerError, e)
+	}
+	glog.V(2).Infoln("new store task =", tid, ", error =", e)
+}
+
+func (vs *VolumeServer) queryTaskHandler(w http.ResponseWriter, r *http.Request) {
+	tid := r.Form.Get("tid")
+	timeoutStr := strings.TrimSpace(r.Form.Get("timeout"))
+	d := time.Minute
+	if td, e := time.ParseDuration(timeoutStr); e == nil {
+		d = td
+	}
+	err := vs.store.TaskManager.QueryResult(tid, d)
+	if err == storage.ErrTaskNotFinish {
+		writeJsonError(w, r, http.StatusRequestTimeout, err)
+	} else if err == nil {
+		writeJsonError(w, r, http.StatusOK, err)
+	}
+	glog.V(2).Infoln("query task =", tid, ", error =", err)
+}
+func (vs *VolumeServer) commitTaskHandler(w http.ResponseWriter, r *http.Request) {
+	tid := r.Form.Get("tid")
+	err := vs.store.TaskManager.Commit(tid)
+	if err == storage.ErrTaskNotFinish {
+		writeJsonError(w, r, http.StatusRequestTimeout, err)
+	} else if err == nil {
+		writeJsonError(w, r, http.StatusOK, err)
+	}
+	glog.V(2).Infoln("query task =", tid, ", error =", err)
+}
+func (vs *VolumeServer) cleanTaskHandler(w http.ResponseWriter, r *http.Request) {
+	tid := r.Form.Get("tid")
+	err := vs.store.TaskManager.Clean(tid)
+	if err == storage.ErrTaskNotFinish {
+		writeJsonError(w, r, http.StatusRequestTimeout, err)
+	} else if err == nil {
+		writeJsonError(w, r, http.StatusOK, err)
+	}
+	glog.V(2).Infoln("clean task =", tid, ", error =", err)
+}
+
+func (vs *VolumeServer) allTaskHandler(w http.ResponseWriter, r *http.Request) {
+	//TODO get all task
+	glog.V(2).Infoln("TODO: get all task")
+}