diff --git a/weed-fs/src/cmd/weed/master.go b/weed-fs/src/cmd/weed/master.go
index c60974a67..151ae31fc 100644
--- a/weed-fs/src/cmd/weed/master.go
+++ b/weed-fs/src/cmd/weed/master.go
@@ -107,8 +107,14 @@ func dirJoinHandler(w http.ResponseWriter, r *http.Request) {
 	if ip == "" {
 		ip = r.RemoteAddr[0:strings.Index(r.RemoteAddr, ":")]
 	}
-	port, _ := strconv.Atoi(r.FormValue("port"))
-	maxVolumeCount, _ := strconv.Atoi(r.FormValue("maxVolumeCount"))
+	port, err := strconv.Atoi(r.FormValue("port"))
+	if err != nil {
+		log.Printf("ERROR bad port number %s: %s", r.FormValue("port"), err)
+	}
+	maxVolumeCount, err := strconv.Atoi(r.FormValue("maxVolumeCount"))
+	if err != nil {
+		log.Printf("ERROR bad maxVolumeCount %s: %s", r.FormValue("maxVolumeCount"), err)
+	}
 	s := r.RemoteAddr[0:strings.Index(r.RemoteAddr, ":")+1] + r.FormValue("port")
 	publicUrl := r.FormValue("publicUrl")
 	volumes := new([]storage.VolumeInfo)
diff --git a/weed-fs/src/pkg/storage/needle_map.go b/weed-fs/src/pkg/storage/needle_map.go
index 9d7369509..f103d10d8 100644
--- a/weed-fs/src/pkg/storage/needle_map.go
+++ b/weed-fs/src/pkg/storage/needle_map.go
@@ -1,6 +1,7 @@
 package storage
 
 import (
+	"errors"
 	"io"
 	"log"
 	"os"
@@ -60,10 +61,16 @@ func NewFrozenNeedleMap(file *os.File) (*NeedleMap, error) {
 	}, nil
 }
 
+func (nm NeedleMap) IsFrozen() bool {
+	return nm.m == nil && nm.fm != nil
+}
+
 const (
 	RowsToRead = 1024
 )
 
+var MapIsFrozen = errors.New("Map is frozen!")
+
 func LoadNeedleMap(file *os.File) (*NeedleMap, error) {
 	nm := NewNeedleMap(file)
 
@@ -124,6 +131,9 @@ func readIndexFile(indexFile *os.File, iterFun func([]byte) error) error {
 }
 
 func (nm *NeedleMap) Put(key uint64, offset uint32, size uint32) (int, error) {
+	if nm.IsFrozen() {
+		return 0, MapIsFrozen
+	}
 	oldSize := nm.m.Set(Key(key), offset, size)
 	util.Uint64toBytes(nm.bytes[0:8], key)
 	util.Uint32toBytes(nm.bytes[8:12], offset)
@@ -140,13 +150,17 @@ func (nm *NeedleMap) Get(key uint64) (element *NeedleValue, ok bool) {
 	element, ok = nm.m.Get(Key(key))
 	return
 }
-func (nm *NeedleMap) Delete(key uint64) {
+func (nm *NeedleMap) Delete(key uint64) error {
+	if nm.IsFrozen() {
+		return MapIsFrozen
+	}
 	nm.deletionByteCounter = nm.deletionByteCounter + uint64(nm.m.Delete(Key(key)))
 	util.Uint64toBytes(nm.bytes[0:8], key)
 	util.Uint32toBytes(nm.bytes[8:12], 0)
 	util.Uint32toBytes(nm.bytes[12:16], 0)
 	nm.indexFile.Write(nm.bytes)
 	nm.deletionCounter++
+	return nil
 }
 func (nm *NeedleMap) Close() {
 	nm.indexFile.Close()
diff --git a/weed-fs/src/pkg/storage/store.go b/weed-fs/src/pkg/storage/store.go
index 79cf65e28..b06c29902 100644
--- a/weed-fs/src/pkg/storage/store.go
+++ b/weed-fs/src/pkg/storage/store.go
@@ -120,8 +120,16 @@ func (s *Store) loadExistingVolumes() {
 func (s *Store) Status() []*VolumeInfo {
 	var stats []*VolumeInfo
 	for k, v := range s.volumes {
-		s := new(VolumeInfo)
-		s.Id, s.Size, s.RepType, s.Version, s.FileCount, s.DeleteCount, s.DeletedByteCount = VolumeId(k), v.ContentSize(), v.replicaType, v.Version(), v.nm.fileCounter, v.nm.deletionCounter, v.nm.deletionByteCounter
+		s := &VolumeInfo{
+			Id:               VolumeId(k),
+			Size:             v.ContentSize(),
+			RepType:          v.replicaType,
+			Version:          v.Version(),
+			FileCount:        v.nm.fileCounter,
+			DeleteCount:      v.nm.deletionCounter,
+			DeletedByteCount: v.nm.deletionByteCounter,
+			Frozen:           !v.IsWritable(),
+		}
 		stats = append(stats, s)
 	}
 	return stats
@@ -134,6 +142,8 @@ type JoinResult struct {
 func (s *Store) SetMaster(mserver string) {
 	s.masterNode = mserver
 }
+
+// call master's /dir/join
 func (s *Store) Join() error {
 	stats := new([]*VolumeInfo)
 	for k, v := range s.volumes {
@@ -171,7 +181,8 @@ func (s *Store) Close() {
 func (s *Store) Write(i VolumeId, n *Needle) uint32 {
 	if v := s.volumes[i]; v != nil {
 		size := v.write(n)
-		if s.volumeSizeLimit < v.ContentSize()+uint64(size) && s.volumeSizeLimit >= v.ContentSize() {
+		if s.volumeSizeLimit < v.ContentSize()+uint64(size) &&
+			s.volumeSizeLimit >= v.ContentSize() {
 			log.Println("volume", i, "size is", v.ContentSize(), "close to", s.volumeSizeLimit)
 			s.Join()
 		}
diff --git a/weed-fs/src/pkg/storage/volume.go b/weed-fs/src/pkg/storage/volume.go
index 71dfb5aee..6a79d6c40 100644
--- a/weed-fs/src/pkg/storage/volume.go
+++ b/weed-fs/src/pkg/storage/volume.go
@@ -3,6 +3,7 @@ package storage
 import (
 	"errors"
 	"fmt"
+	"log"
 	"os"
 	"path"
 	"sync"
@@ -64,6 +65,18 @@ func (v *Volume) Size() int64 {
 	fmt.Printf("Failed to read file size %s %s\n", v.dataFile.Name(), e.Error())
 	return -1
 }
+
+// a volume is writable, if its data file is writable and the index is not frozen
+func (v *Volume) IsWritable() bool {
+	stat, e := v.dataFile.Stat()
+	if e != nil {
+		log.Printf("Failed to read file permission %s %s\n", v.dataFile.Name(), e.Error())
+		return false
+	}
+	//  4 for r, 2 for w, 1 for x
+	return stat.Mode().Perm()&0222 > 0 && !v.nm.IsFrozen()
+}
+
 func (v *Volume) Close() {
 	v.accessLock.Lock()
 	defer v.accessLock.Unlock()
diff --git a/weed-fs/src/pkg/storage/volume_info.go b/weed-fs/src/pkg/storage/volume_info.go
index e4c5f6ec4..845301670 100644
--- a/weed-fs/src/pkg/storage/volume_info.go
+++ b/weed-fs/src/pkg/storage/volume_info.go
@@ -10,4 +10,5 @@ type VolumeInfo struct {
 	FileCount        int
 	DeleteCount      int
 	DeletedByteCount uint64
+	Frozen           bool
 }
diff --git a/weed-fs/src/pkg/topology/volume_layout.go b/weed-fs/src/pkg/topology/volume_layout.go
index 23802ca81..141a40072 100644
--- a/weed-fs/src/pkg/topology/volume_layout.go
+++ b/weed-fs/src/pkg/topology/volume_layout.go
@@ -45,7 +45,9 @@ func (vl *VolumeLayout) RegisterVolume(v *storage.VolumeInfo, dn *DataNode) {
 }
 
 func (vl *VolumeLayout) isWritable(v *storage.VolumeInfo) bool {
-	return uint64(v.Size) < vl.volumeSizeLimit && v.Version == storage.CurrentVersion
+	return !v.Frozen &&
+		uint64(v.Size) < vl.volumeSizeLimit &&
+		v.Version == storage.CurrentVersion
 }
 
 func (vl *VolumeLayout) Lookup(vid storage.VolumeId) []*DataNode {
@@ -92,6 +94,7 @@ func (vl *VolumeLayout) setVolumeWritable(vid storage.VolumeId) bool {
 			return false
 		}
 	}
+	// FIXME: how to refuse if volume is unwritable/frozen?
 	fmt.Println("Volume", vid, "becomes writable")
 	vl.writables = append(vl.writables, vid)
 	if len(vl.writables) > 1 {