diff --git a/go/replication/volume_growth.go b/go/replication/volume_growth.go
index ce54b1fd4..6b3030293 100644
--- a/go/replication/volume_growth.go
+++ b/go/replication/volume_growth.go
@@ -6,6 +6,7 @@ import (
 	"code.google.com/p/weed-fs/go/topology"
 	"errors"
 	"fmt"
+	"log"
 	"math/rand"
 	"sync"
 )
@@ -106,7 +107,6 @@ func (vg *VolumeGrowth) GrowByCountAndType(count int, repType storage.Replicatio
 			nl := topology.NewNodeList(topo.Children(), nil)
 			picked, ret := nl.RandomlyPickN(2, 1, dataCenter)
 			vid := topo.NextVolumeId()
-			println("growing on picked servers", picked)
 			if ret {
 				var servers []*topology.DataNode
 				for _, n := range picked {
@@ -116,7 +116,6 @@ func (vg *VolumeGrowth) GrowByCountAndType(count int, repType storage.Replicatio
 						}
 					}
 				}
-				println("growing on servers", servers)
 				if len(servers) == 2 {
 					if err = vg.grow(topo, vid, repType, servers...); err == nil {
 						counter++
@@ -193,9 +192,9 @@ func (vg *VolumeGrowth) grow(topo *topology.Topology, vid storage.VolumeId, repT
 			vi := storage.VolumeInfo{Id: vid, Size: 0, RepType: repType, Version: storage.CurrentVersion}
 			server.AddOrUpdateVolume(vi)
 			topo.RegisterVolumeLayout(&vi, server)
-			fmt.Println("Created Volume", vid, "on", server)
+			log.Println("Created Volume", vid, "on", server)
 		} else {
-			fmt.Println("Failed to assign", vid, "to", servers, "error", err)
+			log.Println("Failed to assign", vid, "to", servers, "error", err)
 			return errors.New("Failed to assign " + vid.String())
 		}
 	}
diff --git a/go/storage/needle.go b/go/storage/needle.go
index 9822e5d01..18c4727bc 100644
--- a/go/storage/needle.go
+++ b/go/storage/needle.go
@@ -4,7 +4,7 @@ import (
 	"code.google.com/p/weed-fs/go/util"
 	"encoding/hex"
 	"errors"
-	"fmt"
+	"log"
 	"io/ioutil"
 	"mime"
 	"net/http"
@@ -43,13 +43,13 @@ func NewNeedle(r *http.Request) (n *Needle, e error) {
 	n = new(Needle)
 	form, fe := r.MultipartReader()
 	if fe != nil {
-		fmt.Println("MultipartReader [ERROR]", fe)
+		log.Println("MultipartReader [ERROR]", fe)
 		e = fe
 		return
 	}
 	part, fe := form.NextPart()
 	if fe != nil {
-		fmt.Println("Reading Multi part [ERROR]", fe)
+		log.Println("Reading Multi part [ERROR]", fe)
 		e = fe
 		return
 	}
@@ -114,7 +114,7 @@ func (n *Needle) ParsePath(fid string) {
 	length := len(fid)
 	if length <= 8 {
 		if length > 0 {
-			println("Invalid fid", fid, "length", length)
+			log.Println("Invalid fid", fid, "length", length)
 		}
 		return
 	}
@@ -136,7 +136,7 @@ func ParseKeyHash(key_hash_string string) (uint64, uint32) {
 	key_hash_bytes, khe := hex.DecodeString(key_hash_string)
 	key_hash_len := len(key_hash_bytes)
 	if khe != nil || key_hash_len <= 4 {
-		println("Invalid key_hash", key_hash_string, "length:", key_hash_len, "error", khe)
+		log.Println("Invalid key_hash", key_hash_string, "length:", key_hash_len, "error", khe)
 		return 0, 0
 	}
 	key := util.BytesToUint64(key_hash_bytes[0 : key_hash_len-4])
diff --git a/go/storage/needle_read_write.go b/go/storage/needle_read_write.go
index 721d61942..5c72c5edb 100644
--- a/go/storage/needle_read_write.go
+++ b/go/storage/needle_read_write.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"os"
 )
 
@@ -26,7 +27,7 @@ func (n *Needle) Append(w io.Writer, version Version) (size uint32, err error) {
 			defer func(s io.Seeker, off int64) {
 				if err != nil {
 					if _, e = s.Seek(off, 0); e != nil {
-						fmt.Printf("Failed to seek %s back to %d with error: %s\n", w, off, e)
+						log.Printf("Failed to seek %s back to %d with error: %s\n", w, off, e)
 					}
 				}
 			}(s, end)
diff --git a/go/storage/volume.go b/go/storage/volume.go
index b03e564ca..bd11f48c6 100644
--- a/go/storage/volume.go
+++ b/go/storage/volume.go
@@ -108,7 +108,7 @@ func (v *Volume) Size() int64 {
 	if e == nil {
 		return stat.Size()
 	}
-	fmt.Printf("Failed to read file size %s %s\n", v.dataFile.Name(), e.Error())
+	log.Printf("Failed to read file size %s %s\n", v.dataFile.Name(), e.Error())
 	return -1
 }
 func (v *Volume) Close() {
@@ -120,7 +120,7 @@ func (v *Volume) Close() {
 func (v *Volume) maybeWriteSuperBlock() error {
 	stat, e := v.dataFile.Stat()
 	if e != nil {
-		fmt.Printf("failed to stat datafile %s: %s", v.dataFile, e)
+		log.Printf("failed to stat datafile %s: %s", v.dataFile, e)
 		return e
 	}
 	if stat.Size() == 0 {
diff --git a/go/topology/node.go b/go/topology/node.go
index d61f01244..b2414032b 100644
--- a/go/topology/node.go
+++ b/go/topology/node.go
@@ -2,7 +2,7 @@ package topology
 
 import (
 	"code.google.com/p/weed-fs/go/storage"
-	"fmt"
+	"log"
 )
 
 type NodeId string
@@ -155,7 +155,7 @@ func (n *NodeImpl) LinkChildNode(node Node) {
 		n.UpAdjustVolumeCountDelta(node.GetVolumeCount())
 		n.UpAdjustActiveVolumeCountDelta(node.GetActiveVolumeCount())
 		node.SetParent(n)
-		fmt.Println(n, "adds child", node.Id())
+		log.Println(n, "adds child", node.Id())
 	}
 }
 
@@ -167,7 +167,7 @@ func (n *NodeImpl) UnlinkChildNode(nodeId NodeId) {
 		n.UpAdjustVolumeCountDelta(-node.GetVolumeCount())
 		n.UpAdjustActiveVolumeCountDelta(-node.GetActiveVolumeCount())
 		n.UpAdjustMaxVolumeCountDelta(-node.GetMaxVolumeCount())
-		fmt.Println(n, "removes", node, "volumeCount =", n.activeVolumeCount)
+		log.Println(n, "removes", node, "volumeCount =", n.activeVolumeCount)
 	}
 }
 
diff --git a/go/topology/node_list.go b/go/topology/node_list.go
index 2be90b123..9dfc5fded 100644
--- a/go/topology/node_list.go
+++ b/go/topology/node_list.go
@@ -2,7 +2,7 @@ package topology
 
 import (
 	"code.google.com/p/weed-fs/go/storage"
-	"fmt"
+	"log"
 	"math/rand"
 )
 
@@ -58,7 +58,7 @@ func (nl *NodeList) RandomlyPickN(count int, minSpace int, firstNodeName string)
 		list[r], list[i-1] = list[i-1], list[r]
 	}
 	if firstNodeName != "" {
-	  list[0] = *preferredNode
+		list[0] = *preferredNode
 	}
 	return list[:count], true
 }
@@ -70,7 +70,7 @@ func (nl *NodeList) ReserveOneVolume(randomVolumeIndex int, vid storage.VolumeId
 			randomVolumeIndex -= freeSpace
 		} else {
 			if node.IsDataNode() && node.FreeSpace() > 0 {
-				fmt.Println("vid =", vid, " assigned to node =", node, ", freeSpace =", node.FreeSpace())
+				log.Println("vid =", vid, " assigned to node =", node, ", freeSpace =", node.FreeSpace())
 				return true, node.(*DataNode)
 			}
 			children := node.Children()
diff --git a/go/topology/topology.go b/go/topology/topology.go
index e488319d1..b3223c5b4 100644
--- a/go/topology/topology.go
+++ b/go/topology/topology.go
@@ -4,7 +4,6 @@ import (
 	"code.google.com/p/weed-fs/go/sequence"
 	"code.google.com/p/weed-fs/go/storage"
 	"errors"
-	"fmt"
 	"io/ioutil"
 	"log"
 	"math/rand"
@@ -74,7 +73,7 @@ func (t *Topology) Lookup(vid storage.VolumeId) []*DataNode {
 
 func (t *Topology) RandomlyReserveOneVolume(dataCenter string) (bool, *DataNode, *storage.VolumeId) {
 	if t.FreeSpace() <= 0 {
-		fmt.Println("Topology does not have free space left!")
+		log.Println("Topology does not have free space left!")
 		return false, nil, nil
 	}
 	vid := t.NextVolumeId()
@@ -103,7 +102,7 @@ func (t *Topology) PickForWrite(repType storage.ReplicationType, count int, data
 func (t *Topology) GetVolumeLayout(repType storage.ReplicationType) *VolumeLayout {
 	replicationTypeIndex := repType.GetReplicationLevelIndex()
 	if t.replicaType2VolumeLayout[replicationTypeIndex] == nil {
-		fmt.Println("adding replication type", repType)
+		log.Println("adding replication type", repType)
 		t.replicaType2VolumeLayout[replicationTypeIndex] = NewVolumeLayout(repType, t.volumeSizeLimit, t.pulse)
 	}
 	return t.replicaType2VolumeLayout[replicationTypeIndex]
diff --git a/go/topology/topology_compact.go b/go/topology/topology_compact.go
index 7215edc4e..1e5c4dd11 100644
--- a/go/topology/topology_compact.go
+++ b/go/topology/topology_compact.go
@@ -5,7 +5,7 @@ import (
 	"code.google.com/p/weed-fs/go/util"
 	"encoding/json"
 	"errors"
-	"fmt"
+	"log"
 	"net/url"
 	"time"
 )
@@ -14,12 +14,12 @@ func batchVacuumVolumeCheck(vl *VolumeLayout, vid storage.VolumeId, locationlist
 	ch := make(chan bool, locationlist.Length())
 	for index, dn := range locationlist.list {
 		go func(index int, url string, vid storage.VolumeId) {
-			//fmt.Println(index, "Check vacuuming", vid, "on", dn.Url())
+			//log.Println(index, "Check vacuuming", vid, "on", dn.Url())
 			if e, ret := vacuumVolume_Check(url, vid, garbageThreshold); e != nil {
-				//fmt.Println(index, "Error when checking vacuuming", vid, "on", url, e)
+				//log.Println(index, "Error when checking vacuuming", vid, "on", url, e)
 				ch <- false
 			} else {
-				//fmt.Println(index, "Checked vacuuming", vid, "on", url, "needVacuum", ret)
+				//log.Println(index, "Checked vacuuming", vid, "on", url, "needVacuum", ret)
 				ch <- ret
 			}
 		}(index, dn.Url(), vid)
@@ -41,12 +41,12 @@ func batchVacuumVolumeCompact(vl *VolumeLayout, vid storage.VolumeId, locationli
 	ch := make(chan bool, locationlist.Length())
 	for index, dn := range locationlist.list {
 		go func(index int, url string, vid storage.VolumeId) {
-			fmt.Println(index, "Start vacuuming", vid, "on", url)
+			log.Println(index, "Start vacuuming", vid, "on", url)
 			if e := vacuumVolume_Compact(url, vid); e != nil {
-				fmt.Println(index, "Error when vacuuming", vid, "on", url, e)
+				log.Println(index, "Error when vacuuming", vid, "on", url, e)
 				ch <- false
 			} else {
-				fmt.Println(index, "Complete vacuuming", vid, "on", url)
+				log.Println(index, "Complete vacuuming", vid, "on", url)
 				ch <- true
 			}
 		}(index, dn.Url(), vid)
@@ -65,12 +65,12 @@ func batchVacuumVolumeCompact(vl *VolumeLayout, vid storage.VolumeId, locationli
 func batchVacuumVolumeCommit(vl *VolumeLayout, vid storage.VolumeId, locationlist *VolumeLocationList) bool {
 	isCommitSuccess := true
 	for _, dn := range locationlist.list {
-		fmt.Println("Start Commiting vacuum", vid, "on", dn.Url())
+		log.Println("Start Commiting vacuum", vid, "on", dn.Url())
 		if e := vacuumVolume_Commit(dn.Url(), vid); e != nil {
-			fmt.Println("Error when committing vacuum", vid, "on", dn.Url(), e)
+			log.Println("Error when committing vacuum", vid, "on", dn.Url(), e)
 			isCommitSuccess = false
 		} else {
-			fmt.Println("Complete Commiting vacuum", vid, "on", dn.Url())
+			log.Println("Complete Commiting vacuum", vid, "on", dn.Url())
 		}
 	}
 	if isCommitSuccess {
@@ -104,7 +104,7 @@ func vacuumVolume_Check(urlLocation string, vid storage.VolumeId, garbageThresho
 	values.Add("garbageThreshold", garbageThreshold)
 	jsonBlob, err := util.Post("http://"+urlLocation+"/admin/vacuum_volume_check", values)
 	if err != nil {
-		fmt.Println("parameters:", values)
+		log.Println("parameters:", values)
 		return err, false
 	}
 	var ret VacuumVolumeResult
diff --git a/go/topology/topology_event_handling.go b/go/topology/topology_event_handling.go
index fd2fe3bef..fff9b47c8 100644
--- a/go/topology/topology_event_handling.go
+++ b/go/topology/topology_event_handling.go
@@ -2,7 +2,7 @@ package topology
 
 import (
 	"code.google.com/p/weed-fs/go/storage"
-	"fmt"
+	"log"
 	"math/rand"
 	"time"
 )
@@ -28,10 +28,10 @@ func (t *Topology) StartRefreshWritableVolumes(garbageThreshold string) {
 				t.SetVolumeCapacityFull(v)
 			case dn := <-t.chanRecoveredDataNodes:
 				t.RegisterRecoveredDataNode(dn)
-				fmt.Println("DataNode", dn, "is back alive!")
+				log.Println("DataNode", dn, "is back alive!")
 			case dn := <-t.chanDeadDataNodes:
 				t.UnRegisterDataNode(dn)
-				fmt.Println("DataNode", dn, "is dead!")
+				log.Println("DataNode", dn, "is dead!")
 			}
 		}
 	}()
@@ -48,7 +48,7 @@ func (t *Topology) SetVolumeCapacityFull(volumeInfo storage.VolumeInfo) bool {
 }
 func (t *Topology) UnRegisterDataNode(dn *DataNode) {
 	for _, v := range dn.volumes {
-		fmt.Println("Removing Volume", v.Id, "from the dead volume server", dn)
+		log.Println("Removing Volume", v.Id, "from the dead volume server", dn)
 		vl := t.GetVolumeLayout(v.RepType)
 		vl.SetVolumeUnavailable(dn, v.Id)
 	}
diff --git a/go/topology/volume_layout.go b/go/topology/volume_layout.go
index d8ed49b0b..7d7e3f662 100644
--- a/go/topology/volume_layout.go
+++ b/go/topology/volume_layout.go
@@ -3,7 +3,7 @@ package topology
 import (
 	"code.google.com/p/weed-fs/go/storage"
 	"errors"
-	"fmt"
+	"log"
 	"math/rand"
 )
 
@@ -54,7 +54,7 @@ func (vl *VolumeLayout) Lookup(vid storage.VolumeId) []*DataNode {
 func (vl *VolumeLayout) PickForWrite(count int, dataCenter string) (*storage.VolumeId, int, *VolumeLocationList, error) {
 	len_writers := len(vl.writables)
 	if len_writers <= 0 {
-		fmt.Println("No more writable volumes!")
+		log.Println("No more writable volumes!")
 		return nil, 0, nil, errors.New("No more writable volumes!")
 	}
 	if dataCenter == "" {
@@ -102,7 +102,7 @@ func (vl *VolumeLayout) GetActiveVolumeCount(dataCenter string) int {
 func (vl *VolumeLayout) removeFromWritable(vid storage.VolumeId) bool {
 	for i, v := range vl.writables {
 		if v == vid {
-			fmt.Println("Volume", vid, "becomes unwritable")
+			log.Println("Volume", vid, "becomes unwritable")
 			vl.writables = append(vl.writables[:i], vl.writables[i+1:]...)
 			return true
 		}
@@ -115,7 +115,7 @@ func (vl *VolumeLayout) setVolumeWritable(vid storage.VolumeId) bool {
 			return false
 		}
 	}
-	fmt.Println("Volume", vid, "becomes writable")
+	log.Println("Volume", vid, "becomes writable")
 	vl.writables = append(vl.writables, vid)
 	return true
 }
@@ -123,7 +123,7 @@ func (vl *VolumeLayout) setVolumeWritable(vid storage.VolumeId) bool {
 func (vl *VolumeLayout) SetVolumeUnavailable(dn *DataNode, vid storage.VolumeId) bool {
 	if vl.vid2location[vid].Remove(dn) {
 		if vl.vid2location[vid].Length() < vl.repType.GetCopyCount() {
-			fmt.Println("Volume", vid, "has", vl.vid2location[vid].Length(), "replica, less than required", vl.repType.GetCopyCount())
+			log.Println("Volume", vid, "has", vl.vid2location[vid].Length(), "replica, less than required", vl.repType.GetCopyCount())
 			return vl.removeFromWritable(vid)
 		}
 	}