diff --git a/weed-fs/src/cmd/weed/master.go b/weed-fs/src/cmd/weed/master.go
index d359152f7..5b69b3d12 100644
--- a/weed-fs/src/cmd/weed/master.go
+++ b/weed-fs/src/cmd/weed/master.go
@@ -47,7 +47,7 @@ func dirLookupHandler(w http.ResponseWriter, r *http.Request) {
 	}
 	volumeId, _ := storage.NewVolumeId(vid)
 	machines := topo.Lookup(volumeId)
-	if machines == nil {
+	if machines != nil {
 		ret := []map[string]string{}
 		for _, dn := range *machines {
 			ret = append(ret, map[string]string{"url": dn.Ip + strconv.Itoa(dn.Port), "publicUrl": dn.PublicUrl})
diff --git a/weed-fs/src/cmd/weed/upload.go b/weed-fs/src/cmd/weed/upload.go
index 01f3e1658..faed646f1 100644
--- a/weed-fs/src/cmd/weed/upload.go
+++ b/weed-fs/src/cmd/weed/upload.go
@@ -42,7 +42,7 @@ func assign(count int) (*AssignResult, error) {
 	values := make(url.Values)
 	values.Add("count", strconv.Itoa(count))
 	values.Add("replication", *uploadReplication)
-	jsonBlob, err := util.Post("http://"+*server+"/dir/assign2", values)
+	jsonBlob, err := util.Post("http://"+*server+"/dir/assign", values)
 	if *IsDebug {
 		fmt.Println("debug", *IsDebug, "assign result :", string(jsonBlob))
 	}
diff --git a/weed-fs/src/cmd/weed/volume.go b/weed-fs/src/cmd/weed/volume.go
index 9c8302629..a6d3e613a 100644
--- a/weed-fs/src/cmd/weed/volume.go
+++ b/weed-fs/src/cmd/weed/volume.go
@@ -79,6 +79,7 @@ func GetHandler(w http.ResponseWriter, r *http.Request) {
 		if err == nil {
 			http.Redirect(w, r, "http://"+lookupResult.Locations[0].PublicUrl+r.URL.Path, http.StatusMovedPermanently)
 		} else {
+    log.Println("lookup error:", err)
 			w.WriteHeader(http.StatusNotFound)
 		}
 		return
@@ -89,6 +90,7 @@ func GetHandler(w http.ResponseWriter, r *http.Request) {
 		log.Println("read bytes", count, "error", e)
 	}
 	if e != nil || count <= 0 {
+    log.Println("read error:", e)
 		w.WriteHeader(http.StatusNotFound)
 		return
 	}
diff --git a/weed-fs/src/pkg/storage/crc.go b/weed-fs/src/pkg/storage/crc.go
new file mode 100644
index 000000000..198352e68
--- /dev/null
+++ b/weed-fs/src/pkg/storage/crc.go
@@ -0,0 +1,21 @@
+package storage
+
+import (
+	"hash/crc32"
+)
+
+var table = crc32.MakeTable(crc32.Castagnoli)
+
+type CRC uint32
+
+func NewCRC(b []byte) CRC {
+	return CRC(0).Update(b)
+}
+
+func (c CRC) Update(b []byte) CRC {
+	return CRC(crc32.Update(uint32(c), table, b))
+}
+
+func (c CRC) Value() uint32 {
+	return uint32(c>>15|c<<17) + 0xa282ead8
+}
diff --git a/weed-fs/src/pkg/storage/needle.go b/weed-fs/src/pkg/storage/needle.go
index d4db281dc..49cceb1d6 100644
--- a/weed-fs/src/pkg/storage/needle.go
+++ b/weed-fs/src/pkg/storage/needle.go
@@ -2,6 +2,7 @@ package storage
 
 import (
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -18,7 +19,7 @@ type Needle struct {
 	Id       uint64 "needle id"
 	Size     uint32 "Data size"
 	Data     []byte "The actual file data"
-	Checksum int32  "CRC32 to check integrity"
+	Checksum CRC  "CRC32 to check integrity"
 	Padding  []byte "Aligned to 8 bytes"
 }
 
@@ -44,6 +45,7 @@ func NewNeedle(r *http.Request) (n *Needle, fname string, e error) {
 		}
 	}
 	n.Data = data
+	n.Checksum = NewCRC(data)
 
 	commaSep := strings.LastIndex(r.URL.Path, ",")
 	dotSep := strings.LastIndex(r.URL.Path, ".")
@@ -86,7 +88,8 @@ func (n *Needle) Append(w io.Writer) uint32 {
 	w.Write(header)
 	w.Write(n.Data)
 	rest := 8 - ((n.Size + 16 + 4) % 8)
-	util.Uint32toBytes(header[0:4], uint32(n.Checksum))
+	util.Uint32toBytes(header[0:4], n.Checksum.Value())
+  println("writing checksum", n.Checksum.Value(), "=>", util.BytesToUint32(header[0:4]), "for", n.Id)
 	w.Write(header[0 : rest+4])
 	return n.Size
 }
@@ -97,7 +100,10 @@ func (n *Needle) Read(r io.Reader, size uint32) (int, error) {
 	n.Id = util.BytesToUint64(bytes[4:12])
 	n.Size = util.BytesToUint32(bytes[12:16])
 	n.Data = bytes[16 : 16+size]
-	n.Checksum = int32(util.BytesToUint32(bytes[16+size : 16+size+4]))
+  checksum := util.BytesToUint32(bytes[16+size : 16+size+4])	
+	if checksum != NewCRC(n.Data).Value() {
+	  return 0, errors.New("CRC error! Data On Disk Corrupted!")
+	}
 	return ret, e
 }
 func ReadNeedle(r *os.File) (*Needle, uint32) {