diff --git a/weed/storage/disk_location.go b/weed/storage/disk_location.go
index cc3c83b63..fc11a411f 100644
--- a/weed/storage/disk_location.go
+++ b/weed/storage/disk_location.go
@@ -3,6 +3,7 @@ package storage
 import (
 	"io/ioutil"
 	"strings"
+	"sync"
 
 	"github.com/chrislusf/seaweedfs/weed/glog"
 )
@@ -11,6 +12,7 @@ type DiskLocation struct {
 	Directory      string
 	MaxVolumeCount int
 	volumes        map[VolumeId]*Volume
+	sync.RWMutex
 }
 
 func NewDiskLocation(dir string, maxVolumeCount int) *DiskLocation {
@@ -20,6 +22,8 @@ func NewDiskLocation(dir string, maxVolumeCount int) *DiskLocation {
 }
 
 func (l *DiskLocation) loadExistingVolumes(needleMapKind NeedleMapType) {
+	l.Lock()
+	defer l.Unlock()
 
 	if dirs, err := ioutil.ReadDir(l.Directory); err == nil {
 		for _, dir := range dirs {
@@ -48,6 +52,9 @@ func (l *DiskLocation) loadExistingVolumes(needleMapKind NeedleMapType) {
 }
 
 func (l *DiskLocation) DeleteCollectionFromDiskLocation(collection string) (e error) {
+	l.Lock()
+	defer l.Unlock()
+
 	for k, v := range l.volumes {
 		if v.Collection == collection {
 			e = l.deleteVolumeById(k)
@@ -71,3 +78,35 @@ func (l *DiskLocation) deleteVolumeById(vid VolumeId) (e error) {
 	delete(l.volumes, vid)
 	return
 }
+
+func (l *DiskLocation) SetVolume(vid VolumeId, volume *Volume) {
+	l.Lock()
+	defer l.Unlock()
+
+	l.volumes[vid] = volume
+}
+
+func (l *DiskLocation) FindVolume(vid VolumeId) (*Volume, bool) {
+	l.RLock()
+	defer l.RUnlock()
+
+	v, ok := l.volumes[vid]
+	return v, ok
+}
+
+func (l *DiskLocation) VolumesLen() int {
+	l.RLock()
+	defer l.RUnlock()
+
+	return len(l.volumes)
+}
+
+func (l *DiskLocation) Close() {
+	l.Lock()
+	defer l.Unlock()
+
+	for _, v := range l.volumes {
+		v.Close()
+	}
+	return
+}
diff --git a/weed/storage/store.go b/weed/storage/store.go
index d6c7172e7..614c87ace 100644
--- a/weed/storage/store.go
+++ b/weed/storage/store.go
@@ -143,7 +143,7 @@ func (s *Store) DeleteCollection(collection string) (e error) {
 
 func (s *Store) findVolume(vid VolumeId) *Volume {
 	for _, location := range s.Locations {
-		if v, found := location.volumes[vid]; found {
+		if v, found := location.FindVolume(vid); found {
 			return v
 		}
 	}
@@ -152,7 +152,7 @@ func (s *Store) findVolume(vid VolumeId) *Volume {
 func (s *Store) findFreeLocation() (ret *DiskLocation) {
 	max := 0
 	for _, location := range s.Locations {
-		currentFreeCount := location.MaxVolumeCount - len(location.volumes)
+		currentFreeCount := location.MaxVolumeCount - location.VolumesLen()
 		if currentFreeCount > max {
 			max = currentFreeCount
 			ret = location
@@ -168,7 +168,7 @@ func (s *Store) addVolume(vid VolumeId, collection string, needleMapKind NeedleM
 		glog.V(0).Infof("In dir %s adds volume:%v collection:%s replicaPlacement:%v ttl:%v",
 			location.Directory, vid, collection, replicaPlacement, ttl)
 		if volume, err := NewVolume(location.Directory, collection, vid, needleMapKind, replicaPlacement, ttl); err == nil {
-			location.volumes[vid] = volume
+			location.SetVolume(vid, volume)
 			return nil
 		} else {
 			return err
@@ -180,6 +180,7 @@ func (s *Store) addVolume(vid VolumeId, collection string, needleMapKind NeedleM
 func (s *Store) Status() []*VolumeInfo {
 	var stats []*VolumeInfo
 	for _, location := range s.Locations {
+		location.RLock()
 		for k, v := range location.volumes {
 			s := &VolumeInfo{
 				Id:               VolumeId(k),
@@ -194,6 +195,7 @@ func (s *Store) Status() []*VolumeInfo {
 				Ttl:              v.Ttl}
 			stats = append(stats, s)
 		}
+		location.RUnlock()
 	}
 	sortVolumeInfos(stats)
 	return stats
@@ -219,6 +221,7 @@ func (s *Store) SendHeartbeatToMaster() (masterNode string, secretKey security.S
 	var maxFileKey uint64
 	for _, location := range s.Locations {
 		maxVolumeCount = maxVolumeCount + location.MaxVolumeCount
+		location.Lock()
 		for k, v := range location.volumes {
 			if maxFileKey < v.nm.MaxFileKey() {
 				maxFileKey = v.nm.MaxFileKey()
@@ -246,6 +249,7 @@ func (s *Store) SendHeartbeatToMaster() (masterNode string, secretKey security.S
 				}
 			}
 		}
+		location.Unlock()
 	}
 
 	joinMessage := &operation.JoinMessage{
@@ -290,9 +294,7 @@ func (s *Store) SendHeartbeatToMaster() (masterNode string, secretKey security.S
 }
 func (s *Store) Close() {
 	for _, location := range s.Locations {
-		for _, v := range location.volumes {
-			v.Close()
-		}
+		location.Close()
 	}
 }
 func (s *Store) Write(i VolumeId, n *Needle) (size uint32, err error) {