diff --git a/command.go b/command.go
index 1c014e4d0..9ab35934b 100644
--- a/command.go
+++ b/command.go
@@ -9,7 +9,7 @@ import (
 	"time"
 
 	etcdErr "github.com/coreos/etcd/error"
-	"github.com/coreos/etcd/file_system"
+	"github.com/coreos/etcd/store"
 	"github.com/coreos/go-raft"
 )
 
@@ -39,7 +39,7 @@ func (c *CreateCommand) CommandName() string {
 
 // Create node
 func (c *CreateCommand) Apply(server *raft.Server) (interface{}, error) {
-	e, err := etcdFs.Create(c.Key, c.Value, c.ExpireTime, server.CommitIndex(), server.Term())
+	e, err := etcdStore.Create(c.Key, c.Value, c.ExpireTime, server.CommitIndex(), server.Term())
 
 	if err != nil {
 		debug(err)
@@ -63,7 +63,7 @@ func (c *UpdateCommand) CommandName() string {
 
 // Update node
 func (c *UpdateCommand) Apply(server *raft.Server) (interface{}, error) {
-	e, err := etcdFs.Update(c.Key, c.Value, c.ExpireTime, server.CommitIndex(), server.Term())
+	e, err := etcdStore.Update(c.Key, c.Value, c.ExpireTime, server.CommitIndex(), server.Term())
 
 	if err != nil {
 		debug(err)
@@ -89,7 +89,7 @@ func (c *TestAndSetCommand) CommandName() string {
 
 // Set the key-value pair if the current value of the key equals to the given prevValue
 func (c *TestAndSetCommand) Apply(server *raft.Server) (interface{}, error) {
-	e, err := etcdFs.TestAndSet(c.Key, c.PrevValue, c.PrevIndex,
+	e, err := etcdStore.TestAndSet(c.Key, c.PrevValue, c.PrevIndex,
 		c.Value, c.ExpireTime, server.CommitIndex(), server.Term())
 
 	if err != nil {
@@ -114,7 +114,7 @@ func (c *GetCommand) CommandName() string {
 
 // Get the value of key
 func (c *GetCommand) Apply(server *raft.Server) (interface{}, error) {
-	e, err := etcdFs.Get(c.Key, c.Recursive, c.Sorted, server.CommitIndex(), server.Term())
+	e, err := etcdStore.Get(c.Key, c.Recursive, c.Sorted, server.CommitIndex(), server.Term())
 
 	if err != nil {
 		debug(err)
@@ -137,7 +137,7 @@ func (c *DeleteCommand) CommandName() string {
 
 // Delete the key
 func (c *DeleteCommand) Apply(server *raft.Server) (interface{}, error) {
-	e, err := etcdFs.Delete(c.Key, c.Recursive, server.CommitIndex(), server.Term())
+	e, err := etcdStore.Delete(c.Key, c.Recursive, server.CommitIndex(), server.Term())
 
 	if err != nil {
 		debug(err)
@@ -160,7 +160,7 @@ func (c *WatchCommand) CommandName() string {
 }
 
 func (c *WatchCommand) Apply(server *raft.Server) (interface{}, error) {
-	eventChan, err := etcdFs.Watch(c.Key, c.Recursive, c.SinceIndex, server.CommitIndex(), server.Term())
+	eventChan, err := etcdStore.Watch(c.Key, c.Recursive, c.SinceIndex, server.CommitIndex(), server.Term())
 
 	if err != nil {
 		return nil, err
@@ -197,7 +197,7 @@ func (c *JoinCommand) CommandName() string {
 func (c *JoinCommand) Apply(raftServer *raft.Server) (interface{}, error) {
 
 	// check if the join command is from a previous machine, who lost all its previous log.
-	e, _ := etcdFs.Get(path.Join("/_etcd/machines", c.Name), false, false, raftServer.CommitIndex(), raftServer.Term())
+	e, _ := etcdStore.Get(path.Join("/_etcd/machines", c.Name), false, false, raftServer.CommitIndex(), raftServer.Term())
 
 	b := make([]byte, 8)
 	binary.PutUvarint(b, raftServer.CommitIndex())
@@ -221,7 +221,7 @@ func (c *JoinCommand) Apply(raftServer *raft.Server) (interface{}, error) {
 	// add machine in etcd storage
 	key := path.Join("_etcd/machines", c.Name)
 	value := fmt.Sprintf("raft=%s&etcd=%s&raftVersion=%s", c.RaftURL, c.EtcdURL, c.RaftVersion)
-	etcdFs.Create(key, value, fileSystem.Permanent, raftServer.CommitIndex(), raftServer.Term())
+	etcdStore.Create(key, value, store.Permanent, raftServer.CommitIndex(), raftServer.Term())
 
 	if c.Name != r.Name() { // do not add self to the peer list
 		r.peersStats[c.Name] = &raftPeerStats{MinLatency: 1 << 63}
@@ -250,7 +250,7 @@ func (c *RemoveCommand) Apply(raftServer *raft.Server) (interface{}, error) {
 	// remove machine in etcd storage
 	key := path.Join("_etcd/machines", c.Name)
 
-	_, err := etcdFs.Delete(key, false, raftServer.CommitIndex(), raftServer.Term())
+	_, err := etcdStore.Delete(key, false, raftServer.CommitIndex(), raftServer.Term())
 	delete(r.peersStats, c.Name)
 
 	if err != nil {
diff --git a/error/error.go b/error/error.go
index d97158cf1..643c3244b 100644
--- a/error/error.go
+++ b/error/error.go
@@ -32,27 +32,27 @@ func init() {
 	errors = make(map[int]string)
 
 	// command related errors
-	errors[100] = "Key Not Found"
-	errors[101] = "Test Failed" //test and set
-	errors[102] = "Not A File"
-	errors[103] = "Reached the max number of machines in the cluster"
-	errors[104] = "Not A Directory"
-	errors[105] = "Already exists" // create
-	errors[106] = "The prefix of given key is a keyword in etcd"
+	errors[EcodeKeyNotFound] = "Key Not Found"
+	errors[EcodeTestFailed] = "Test Failed" //test and set
+	errors[EcodeNotFile] = "Not A File"
+	errors[EcodeNoMoreMachine] = "Reached the max number of machines in the cluster"
+	errors[EcodeNotDir] = "Not A Directory"
+	errors[EcodeNodeExist] = "Already exists" // create
+	errors[EcodeKeyIsPreserved] = "The prefix of given key is a keyword in etcd"
 
 	// Post form related errors
-	errors[200] = "Value is Required in POST form"
-	errors[201] = "PrevValue is Required in POST form"
-	errors[202] = "The given TTL in POST form is not a number"
-	errors[203] = "The given index in POST form is not a number"
+	errors[EcodeValueRequired] = "Value is Required in POST form"
+	errors[EcodePrevValueRequired] = "PrevValue is Required in POST form"
+	errors[EcodeTTLNaN] = "The given TTL in POST form is not a number"
+	errors[EcodeIndexNaN] = "The given index in POST form is not a number"
 
 	// raft related errors
-	errors[300] = "Raft Internal Error"
-	errors[301] = "During Leader Election"
+	errors[EcodeRaftInternal] = "Raft Internal Error"
+	errors[EcodeLeaderElect] = "During Leader Election"
 
 	// etcd related errors
-	errors[400] = "watcher is cleared due to etcd recovery"
-	errors[401] = "The event in requested index is outdated and cleared"
+	errors[EcodeWatcherCleared] = "watcher is cleared due to etcd recovery"
+	errors[EcodeEventIndexCleared] = "The event in requested index is outdated and cleared"
 
 }
 
diff --git a/etcd.go b/etcd.go
index cba7809f4..80c8dd122 100644
--- a/etcd.go
+++ b/etcd.go
@@ -10,7 +10,7 @@ import (
 	"strings"
 	"time"
 
-	"github.com/coreos/etcd/file_system"
+	"github.com/coreos/etcd/store"
 	"github.com/coreos/go-raft"
 )
 
@@ -136,7 +136,7 @@ type TLSConfig struct {
 //
 //------------------------------------------------------------------------------
 
-var etcdFs *fileSystem.FileSystem
+var etcdStore *store.Store
 
 //------------------------------------------------------------------------------
 //
@@ -204,7 +204,7 @@ func main() {
 	info := getInfo(dirPath)
 
 	// Create etcd key-value store
-	etcdFs = fileSystem.New()
+	etcdStore = store.New()
 
 	snapConf = newSnapshotConf()
 
diff --git a/etcd_handlers.go b/etcd_handlers.go
index d8f42fc7e..09e5e8252 100644
--- a/etcd_handlers.go
+++ b/etcd_handlers.go
@@ -7,7 +7,7 @@ import (
 	"strings"
 
 	etcdErr "github.com/coreos/etcd/error"
-	"github.com/coreos/etcd/file_system"
+	"github.com/coreos/etcd/store"
 	"github.com/coreos/go-raft"
 )
 
@@ -120,7 +120,7 @@ func UpdateHttpHandler(w http.ResponseWriter, req *http.Request) error {
 	}
 
 	// TODO: update should give at least one option
-	if value == "" && expireTime.Sub(fileSystem.Permanent) == 0 {
+	if value == "" && expireTime.Sub(store.Permanent) == 0 {
 		return nil
 	}
 
@@ -223,8 +223,7 @@ func VersionHttpHandler(w http.ResponseWriter, req *http.Request) error {
 // Handler to return the basic stats of etcd
 func StatsHttpHandler(w http.ResponseWriter, req *http.Request) error {
 	w.WriteHeader(http.StatusOK)
-	//w.Write(etcdStore.Stats())
-	w.Write(etcdFs.Stats.GetStats())
+	w.Write(etcdStore.JsonStats())
 	w.Write(r.Stats())
 	return nil
 }
diff --git a/file_system/stats.go b/file_system/stats.go
deleted file mode 100644
index c05655efc..000000000
--- a/file_system/stats.go
+++ /dev/null
@@ -1,146 +0,0 @@
-package fileSystem
-
-import (
-	"encoding/json"
-	"sync"
-)
-
-const (
-	// Operations that will be running serializely
-	StatsSetsHit         = 100
-	StatsSetsMiss        = 101
-	StatsDeletesHit      = 102
-	StatsDeletesMiss     = 103
-	StatsUpdatesHit      = 104
-	StatsUpdatesMiss     = 105
-	StatsTestAndSetsHit  = 106
-	StatsTestAndSetsMiss = 107
-	StatsRecoveryHit     = 108
-	StatsRecoveryMiss    = 109
-
-	// concurrent operations
-	StatsGetsHit  = 200
-	StatsGetsMiss = 201
-
-	StatsWatchHit      = 300
-	StatsWatchMiss     = 301
-	StatsInWatchingNum = 302
-
-	StatsSaveHit  = 400
-	StatsSaveMiss = 401
-)
-
-type EtcdStats struct {
-
-	// Lock for synchronization
-	rwlock sync.RWMutex
-
-	// Number of get requests
-	GetsHit  uint64 `json:"gets_hits"`
-	GetsMiss uint64 `json:"gets_misses"`
-
-	// Number of sets requests
-	SetsHit  uint64 `json:"sets_hits"`
-	SetsMiss uint64 `json:"sets_misses"`
-
-	// Number of delete requests
-	DeletesHit  uint64 `json:"deletes_hits"`
-	DeletesMiss uint64 `json:"deletes_misses"`
-
-	// Number of update requests
-	UpdatesHit  uint64 `json:"updates_hits"`
-	UpdatesMiss uint64 `json:"updates_misses"`
-
-	// Number of testAndSet requests
-	TestAndSetsHit  uint64 `json:"testAndSets_hits"`
-	TestAndSetsMiss uint64 `json:"testAndSets_misses"`
-
-	// Number of Watch requests
-	WatchHit      uint64 `json:"watch_hit"`
-	WatchMiss     uint64 `json:"watch_miss"`
-	InWatchingNum uint64 `json:"in_watching_number"`
-
-	// Number of save requests
-	SaveHit  uint64 `json:"save_hit"`
-	SaveMiss uint64 `json:"save_miss"`
-
-	// Number of recovery requests
-	RecoveryHit  uint64 `json:"recovery_hit"`
-	RecoveryMiss uint64 `json:"recovery_miss"`
-}
-
-func newStats() *EtcdStats {
-	e := new(EtcdStats)
-	return e
-}
-
-// Status() return the statistics info of etcd storage its recent start
-func (e *EtcdStats) GetStats() []byte {
-	b, _ := json.Marshal(e)
-	return b
-}
-
-func (e *EtcdStats) TotalReads() uint64 {
-	return e.GetsHit + e.GetsMiss
-}
-
-func (e *EtcdStats) TotalWrites() uint64 {
-	return e.SetsHit + e.SetsMiss +
-		e.DeletesHit + e.DeletesMiss +
-		e.UpdatesHit + e.UpdatesMiss +
-		e.TestAndSetsHit + e.TestAndSetsMiss
-}
-
-func (e *EtcdStats) IncStats(field int) {
-	if field >= 200 {
-		e.rwlock.Lock()
-
-		switch field {
-		case StatsGetsHit:
-			e.GetsHit++
-		case StatsGetsMiss:
-			e.GetsMiss++
-		case StatsWatchHit:
-			e.WatchHit++
-		case StatsWatchMiss:
-			e.WatchMiss++
-		case StatsInWatchingNum:
-			e.InWatchingNum++
-		case StatsSaveHit:
-			e.SaveHit++
-		case StatsSaveMiss:
-			e.SaveMiss++
-		}
-
-		e.rwlock.Unlock()
-
-	} else {
-		e.rwlock.RLock()
-
-		switch field {
-		case StatsSetsHit:
-			e.SetsHit++
-		case StatsSetsMiss:
-			e.SetsMiss++
-		case StatsDeletesHit:
-			e.DeletesHit++
-		case StatsDeletesMiss:
-			e.DeletesMiss++
-		case StatsUpdatesHit:
-			e.UpdatesHit++
-		case StatsUpdatesMiss:
-			e.UpdatesMiss++
-		case StatsTestAndSetsHit:
-			e.TestAndSetsHit++
-		case StatsTestAndSetsMiss:
-			e.TestAndSetsMiss++
-		case StatsRecoveryHit:
-			e.RecoveryHit++
-		case StatsRecoveryMiss:
-			e.RecoveryMiss++
-		}
-
-		e.rwlock.RUnlock()
-	}
-
-}
diff --git a/file_system/stats_test.go b/file_system/stats_test.go
deleted file mode 100644
index 38bc42c4f..000000000
--- a/file_system/stats_test.go
+++ /dev/null
@@ -1,221 +0,0 @@
-package fileSystem
-
-import (
-	"math/rand"
-	"testing"
-	"time"
-	//"fmt"
-)
-
-func TestBasicStats(t *testing.T) {
-	fs := New()
-	keys := GenKeys(rand.Intn(100), 5)
-
-	i := uint64(0)
-	GetsHit := uint64(0)
-	GetsMiss := uint64(0)
-	SetsHit := uint64(0)
-	SetsMiss := uint64(0)
-	DeletesHit := uint64(0)
-	DeletesMiss := uint64(0)
-	UpdatesHit := uint64(0)
-	UpdatesMiss := uint64(0)
-	TestAndSetsHit := uint64(0)
-	TestAndSetsMiss := uint64(0)
-	WatchHit := uint64(0)
-	WatchMiss := uint64(0)
-	InWatchingNum := uint64(0)
-	SaveHit := uint64(0)
-	SaveMiss := uint64(0)
-	RecoveryHit := uint64(0)
-	RecoveryMiss := uint64(0)
-
-	for _, k := range keys {
-		i++
-		_, err := fs.Create(k, "bar", time.Now().Add(time.Second*time.Duration(rand.Intn(10))), i, 1)
-		if err != nil {
-			SetsMiss++
-		} else {
-			SetsHit++
-		}
-	}
-
-	for _, k := range keys {
-		_, err := fs.Get(k, false, false, i, 1)
-		if err != nil {
-			GetsMiss++
-		} else {
-			GetsHit++
-		}
-	}
-
-	for _, k := range keys {
-		i++
-		_, err := fs.Update(k, "foo", time.Now().Add(time.Second*time.Duration(rand.Intn(5))), i, 1)
-		if err != nil {
-			UpdatesMiss++
-		} else {
-			UpdatesHit++
-		}
-	}
-
-	for _, k := range keys {
-		_, err := fs.Get(k, false, false, i, 1)
-		if err != nil {
-			GetsMiss++
-		} else {
-			GetsHit++
-		}
-	}
-
-	for _, k := range keys {
-		i++
-		_, err := fs.TestAndSet(k, "foo", 0, "bar", Permanent, i, 1)
-		if err != nil {
-			TestAndSetsMiss++
-		} else {
-			TestAndSetsHit++
-		}
-	}
-
-	//fmt.Printf("#TestAndSet [%d]\n", TestAndSetsHit)
-
-	for _, k := range keys {
-		_, err := fs.Watch(k, false, 0, i, 1)
-		if err != nil {
-			WatchMiss++
-		} else {
-			WatchHit++
-			InWatchingNum++
-		}
-	}
-
-	//fmt.Printf("#Watch [%d]\n", WatchHit)
-
-	for _, k := range keys {
-		_, err := fs.Get(k, false, false, i, 1)
-		if err != nil {
-			GetsMiss++
-		} else {
-			GetsHit++
-		}
-	}
-
-	//fmt.Println("fs.index ", fs.Index)
-	for j := 0; j < 5; j++ {
-		b := make([]byte, 10)
-		err := fs.Recovery(b)
-		if err != nil {
-			RecoveryMiss++
-		}
-
-		b, err = fs.Save()
-		if err != nil {
-			SaveMiss++
-		} else {
-			SaveHit++
-		}
-
-		err = fs.Recovery(b)
-		if err != nil {
-			RecoveryMiss++
-		} else {
-			RecoveryHit++
-		}
-	}
-	//fmt.Println("fs.index after ", fs.Index)
-	//fmt.Println("stats.inwatching ", fs.Stats.InWatchingNum)
-
-	for _, k := range keys {
-		i++
-		_, err := fs.Delete(k, false, i, 1)
-		if err != nil {
-			DeletesMiss++
-		} else {
-			InWatchingNum--
-			DeletesHit++
-		}
-	}
-
-	//fmt.Printf("#Delete [%d] stats.deletehit [%d] \n", DeletesHit, fs.Stats.DeletesHit)
-
-	for _, k := range keys {
-		_, err := fs.Get(k, false, false, i, 1)
-		if err != nil {
-			GetsMiss++
-		} else {
-			GetsHit++
-		}
-	}
-
-	if GetsHit != fs.Stats.GetsHit {
-		t.Fatalf("GetsHit [%d] != Stats.GetsHit [%d]", GetsHit, fs.Stats.GetsHit)
-	}
-
-	if GetsMiss != fs.Stats.GetsMiss {
-		t.Fatalf("GetsMiss [%d] != Stats.GetsMiss [%d]", GetsMiss, fs.Stats.GetsMiss)
-	}
-
-	if SetsHit != fs.Stats.SetsHit {
-		t.Fatalf("SetsHit [%d] != Stats.SetsHit [%d]", SetsHit, fs.Stats.SetsHit)
-	}
-
-	if SetsMiss != fs.Stats.SetsMiss {
-		t.Fatalf("SetsMiss [%d] != Stats.SetsMiss [%d]", SetsMiss, fs.Stats.SetsMiss)
-	}
-
-	if DeletesHit != fs.Stats.DeletesHit {
-		t.Fatalf("DeletesHit [%d] != Stats.DeletesHit [%d]", DeletesHit, fs.Stats.DeletesHit)
-	}
-
-	if DeletesMiss != fs.Stats.DeletesMiss {
-		t.Fatalf("DeletesMiss [%d] != Stats.DeletesMiss [%d]", DeletesMiss, fs.Stats.DeletesMiss)
-	}
-
-	if UpdatesHit != fs.Stats.UpdatesHit {
-		t.Fatalf("UpdatesHit [%d] != Stats.UpdatesHit [%d]", UpdatesHit, fs.Stats.UpdatesHit)
-	}
-
-	if UpdatesMiss != fs.Stats.UpdatesMiss {
-		t.Fatalf("UpdatesMiss [%d] != Stats.UpdatesMiss [%d]", UpdatesMiss, fs.Stats.UpdatesMiss)
-	}
-
-	if TestAndSetsHit != fs.Stats.TestAndSetsHit {
-		t.Fatalf("TestAndSetsHit [%d] != Stats.TestAndSetsHit [%d]", TestAndSetsHit, fs.Stats.TestAndSetsHit)
-	}
-
-	if TestAndSetsMiss != fs.Stats.TestAndSetsMiss {
-		t.Fatalf("TestAndSetsMiss [%d] != Stats.TestAndSetsMiss [%d]", TestAndSetsMiss, fs.Stats.TestAndSetsMiss)
-	}
-
-	if SaveHit != fs.Stats.SaveHit {
-		t.Fatalf("SaveHit [%d] != Stats.SaveHit [%d]", SaveHit, fs.Stats.SaveHit)
-	}
-
-	if SaveMiss != fs.Stats.SaveMiss {
-		t.Fatalf("SaveMiss [%d] != Stats.SaveMiss [%d]", SaveMiss, fs.Stats.SaveMiss)
-	}
-
-	if WatchHit != fs.Stats.WatchHit {
-		t.Fatalf("WatchHit [%d] != Stats.WatchHit [%d]", WatchHit, fs.Stats.WatchHit)
-	}
-
-	if WatchMiss != fs.Stats.WatchMiss {
-		t.Fatalf("WatchMiss [%d] != Stats.WatchMiss [%d]", WatchMiss, fs.Stats.WatchMiss)
-	}
-
-	if InWatchingNum != fs.Stats.InWatchingNum {
-		t.Fatalf("InWatchingNum [%d] != Stats.InWatchingNum [%d]", InWatchingNum, fs.Stats.InWatchingNum)
-	}
-
-	if RecoveryHit != fs.Stats.RecoveryHit {
-		t.Fatalf("RecoveryHit [%d] != Stats.RecoveryHit [%d]", RecoveryHit, fs.Stats.RecoveryHit)
-	}
-
-	if RecoveryMiss != fs.Stats.RecoveryMiss {
-		t.Fatalf("RecoveryMiss [%d] != Stats.RecoveryMiss [%d]", RecoveryMiss, fs.Stats.RecoveryMiss)
-	}
-
-	//fmt.Println(GetsHit, GetsMiss, SetsHit, SetsMiss, DeletesHit, DeletesMiss, UpdatesHit, UpdatesMiss, TestAndSetsHit, TestAndSetsMiss, WatchHit, WatchMiss, InWatchingNum, SaveHit, SaveMiss, RecoveryHit, RecoveryMiss)
-
-}
diff --git a/machines.go b/machines.go
index 1988353d5..b863c50fb 100644
--- a/machines.go
+++ b/machines.go
@@ -2,7 +2,7 @@ package main
 
 // machineNum returns the number of machines in the cluster
 func machineNum() int {
-	e, err := etcdFs.Get("/_etcd/machines", false, false, r.CommitIndex(), r.Term())
+	e, err := etcdStore.Get("/_etcd/machines", false, false, r.CommitIndex(), r.Term())
 
 	if err != nil {
 		return 0
diff --git a/name_url_map.go b/name_url_map.go
index 38e1ecc15..1192f3fda 100644
--- a/name_url_map.go
+++ b/name_url_map.go
@@ -56,7 +56,7 @@ func readURL(nodeName string, urlName string) (string, bool) {
 	// convert nodeName to url from etcd storage
 	key := path.Join("/_etcd/machines", nodeName)
 
-	e, err := etcdFs.Get(key, false, false, r.CommitIndex(), r.Term())
+	e, err := etcdStore.Get(key, false, false, r.CommitIndex(), r.Term())
 
 	if err != nil {
 		return "", false
diff --git a/raft_server.go b/raft_server.go
index d88f266f8..506e4771a 100644
--- a/raft_server.go
+++ b/raft_server.go
@@ -36,7 +36,7 @@ func newRaftServer(name string, url string, listenHost string, tlsConf *TLSConfi
 	raftTransporter := newTransporter(tlsConf.Scheme, tlsConf.Client, ElectionTimeout)
 
 	// Create raft server
-	server, err := raft.NewServer(name, dirPath, raftTransporter, etcdFs, nil)
+	server, err := raft.NewServer(name, dirPath, raftTransporter, etcdStore, nil)
 
 	check(err)
 
diff --git a/file_system/event.go b/store/event.go
similarity index 98%
rename from file_system/event.go
rename to store/event.go
index 3053d85cd..ca7b0389b 100644
--- a/file_system/event.go
+++ b/store/event.go
@@ -1,4 +1,4 @@
-package fileSystem
+package store
 
 import (
 	"fmt"
@@ -6,7 +6,7 @@ import (
 	"sync"
 	"time"
 
-	etcdErr "github.com/xiangli-cmu/etcd/error"
+	etcdErr "github.com/coreos/etcd/error"
 )
 
 const (
diff --git a/file_system/event_test.go b/store/event_test.go
similarity index 98%
rename from file_system/event_test.go
rename to store/event_test.go
index 146f8cd4d..0d19dd52a 100644
--- a/file_system/event_test.go
+++ b/store/event_test.go
@@ -1,4 +1,4 @@
-package fileSystem
+package store
 
 import (
 	"testing"
diff --git a/file_system/node.go b/store/node.go
similarity index 99%
rename from file_system/node.go
rename to store/node.go
index 587cfb430..8502f70d1 100644
--- a/file_system/node.go
+++ b/store/node.go
@@ -1,4 +1,4 @@
-package fileSystem
+package store
 
 import (
 	"path"
@@ -6,7 +6,7 @@ import (
 	"sync"
 	"time"
 
-	etcdErr "github.com/xiangli-cmu/etcd/error"
+	etcdErr "github.com/coreos/etcd/error"
 )
 
 var (
diff --git a/store/stats.go b/store/stats.go
new file mode 100644
index 000000000..1f98625a0
--- /dev/null
+++ b/store/stats.go
@@ -0,0 +1,91 @@
+package store
+
+import (
+	"encoding/json"
+	"sync/atomic"
+)
+
+const (
+	SetSuccess        = 100
+	SetFail           = 101
+	DeleteSuccess     = 102
+	DeleteFail        = 103
+	UpdateSuccess     = 104
+	UpdateFail        = 105
+	TestAndSetSuccess = 106
+	TestAndSetFail    = 107
+	GetSuccess        = 110
+	GetFail           = 111
+)
+
+type Stats struct {
+
+	// Number of get requests
+	GetSuccess uint64 `json:"getsSuccess"`
+	GetFail    uint64 `json:"getsFail"`
+
+	// Number of sets requests
+	SetSuccess uint64 `json:"setsSuccess"`
+	SetFail    uint64 `json:"setsFail"`
+
+	// Number of delete requests
+	DeleteSuccess uint64 `json:"deleteSuccess"`
+	DeleteFail    uint64 `json:"deleteFail"`
+
+	// Number of update requests
+	UpdateSuccess uint64 `json:"updateSuccess"`
+	UpdateFail    uint64 `json:"updateFail"`
+
+	// Number of testAndSet requests
+	TestAndSetSuccess uint64 `json:"testAndSetSuccess"`
+	TestAndSetFail    uint64 `json:"testAndSetFail"`
+
+	Watchers uint64 `json:"watchers"`
+}
+
+func newStats() *Stats {
+	s := new(Stats)
+	return s
+}
+
+// Status() return the statistics info of etcd storage its recent start
+func (s *Stats) toJson() []byte {
+	b, _ := json.Marshal(s)
+	return b
+}
+
+func (s *Stats) TotalReads() uint64 {
+	return s.GetSuccess + s.GetFail
+}
+
+func (s *Stats) TotalWrites() uint64 {
+	return s.SetSuccess + s.SetFail +
+		s.DeleteSuccess + s.DeleteFail +
+		s.TestAndSetSuccess + s.TestAndSetFail +
+		s.UpdateSuccess + s.UpdateFail
+}
+
+func (s *Stats) Inc(field int) {
+	switch field {
+	case SetSuccess:
+		atomic.AddUint64(&s.SetSuccess, 1)
+	case SetFail:
+		atomic.AddUint64(&s.SetFail, 1)
+	case DeleteSuccess:
+		atomic.AddUint64(&s.DeleteSuccess, 1)
+	case DeleteFail:
+		atomic.AddUint64(&s.DeleteFail, 1)
+	case GetSuccess:
+		atomic.AddUint64(&s.GetSuccess, 1)
+	case GetFail:
+		atomic.AddUint64(&s.GetFail, 1)
+	case UpdateSuccess:
+		atomic.AddUint64(&s.UpdateSuccess, 1)
+	case UpdateFail:
+		atomic.AddUint64(&s.UpdateFail, 1)
+	case TestAndSetSuccess:
+		atomic.AddUint64(&s.TestAndSetSuccess, 1)
+	case TestAndSetFail:
+		atomic.AddUint64(&s.TestAndSetFail, 1)
+	}
+}
diff --git a/store/stats_test.go b/store/stats_test.go
new file mode 100644
index 000000000..ff67f328a
--- /dev/null
+++ b/store/stats_test.go
@@ -0,0 +1,139 @@
+package store
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+)
+
+func TestBasicStats(t *testing.T) {
+	s := New()
+	keys := GenKeys(rand.Intn(100), 5)
+
+	var i uint64
+	var GetSuccess, GetFail, SetSuccess, SetFail, DeleteSuccess, DeleteFail uint64
+	var UpdateSuccess, UpdateFail, TestAndSetSuccess, TestAndSetFail, watcher_number uint64
+
+	for _, k := range keys {
+		i++
+		_, err := s.Create(k, "bar", time.Now().Add(time.Second*time.Duration(rand.Intn(10))), i, 1)
+		if err != nil {
+			SetFail++
+		} else {
+			SetSuccess++
+		}
+	}
+
+	for _, k := range keys {
+		_, err := s.Get(k, false, false, i, 1)
+		if err != nil {
+			GetFail++
+		} else {
+			GetSuccess++
+		}
+	}
+
+	for _, k := range keys {
+		i++
+		_, err := s.Update(k, "foo", time.Now().Add(time.Second*time.Duration(rand.Intn(5))), i, 1)
+		if err != nil {
+			UpdateFail++
+		} else {
+			UpdateSuccess++
+		}
+	}
+
+	for _, k := range keys {
+		_, err := s.Get(k, false, false, i, 1)
+		if err != nil {
+			GetFail++
+		} else {
+			GetSuccess++
+		}
+	}
+
+	for _, k := range keys {
+		i++
+		_, err := s.TestAndSet(k, "foo", 0, "bar", Permanent, i, 1)
+		if err != nil {
+			TestAndSetFail++
+		} else {
+			TestAndSetSuccess++
+		}
+	}
+
+	for _, k := range keys {
+		s.Watch(k, false, 0, i, 1)
+		watcher_number++
+	}
+
+	for _, k := range keys {
+		_, err := s.Get(k, false, false, i, 1)
+		if err != nil {
+			GetFail++
+		} else {
+			GetSuccess++
+		}
+	}
+
+	for _, k := range keys {
+		i++
+		_, err := s.Delete(k, false, i, 1)
+		if err != nil {
+			DeleteFail++
+		} else {
+			watcher_number--
+			DeleteSuccess++
+		}
+	}
+
+	for _, k := range keys {
+		_, err := s.Get(k, false, false, i, 1)
+		if err != nil {
+			GetFail++
+		} else {
+			GetSuccess++
+		}
+	}
+
+	if GetSuccess != s.Stats.GetSuccess {
+		t.Fatalf("GetSuccess [%d] != Stats.GetSuccess [%d]", GetSuccess, s.Stats.GetSuccess)
+	}
+
+	if GetFail != s.Stats.GetFail {
+		t.Fatalf("GetFail [%d] != Stats.GetFail [%d]", GetFail, s.Stats.GetFail)
+	}
+
+	if SetSuccess != s.Stats.SetSuccess {
+		t.Fatalf("SetSuccess [%d] != Stats.SetSuccess [%d]", SetSuccess, s.Stats.SetSuccess)
+	}
+
+	if SetFail != s.Stats.SetFail {
+		t.Fatalf("SetFail [%d] != Stats.SetFail [%d]", SetFail, s.Stats.SetFail)
+	}
+
+	if DeleteSuccess != s.Stats.DeleteSuccess {
+		t.Fatalf("DeleteSuccess [%d] != Stats.DeleteSuccess [%d]", DeleteSuccess, s.Stats.DeleteSuccess)
+	}
+
+	if DeleteFail != s.Stats.DeleteFail {
+		t.Fatalf("DeleteFail [%d] != Stats.DeleteFail [%d]", DeleteFail, s.Stats.DeleteFail)
+	}
+
+	if UpdateSuccess != s.Stats.UpdateSuccess {
+		t.Fatalf("UpdateSuccess [%d] != Stats.UpdateSuccess [%d]", UpdateSuccess, s.Stats.UpdateSuccess)
+	}
+
+	if UpdateFail != s.Stats.UpdateFail {
+		t.Fatalf("UpdateFail [%d] != Stats.UpdateFail [%d]", UpdateFail, s.Stats.UpdateFail)
+	}
+
+	if TestAndSetSuccess != s.Stats.TestAndSetSuccess {
+		t.Fatalf("TestAndSetSuccess [%d] != Stats.TestAndSetSuccess [%d]", TestAndSetSuccess, s.Stats.TestAndSetSuccess)
+	}
+
+	if TestAndSetFail != s.Stats.TestAndSetFail {
+		t.Fatalf("TestAndSetFail [%d] != Stats.TestAndSetFail [%d]", TestAndSetFail, s.Stats.TestAndSetFail)
+	}
+
+}
diff --git a/file_system/file_system.go b/store/store.go
similarity index 64%
rename from file_system/file_system.go
rename to store/store.go
index 0ed740253..73c6bf3ec 100644
--- a/file_system/file_system.go
+++ b/store/store.go
@@ -1,4 +1,4 @@
-package fileSystem
+package store
 
 import (
 	"encoding/json"
@@ -8,34 +8,34 @@ import (
 	"strings"
 	"time"
 
-	etcdErr "github.com/xiangli-cmu/etcd/error"
+	etcdErr "github.com/coreos/etcd/error"
 )
 
-type FileSystem struct {
+type Store struct {
 	Root       *Node
 	WatcherHub *watcherHub
 	Index      uint64
 	Term       uint64
-	Stats      *EtcdStats
+	Stats      *Stats
 }
 
-func New() *FileSystem {
-	fs := new(FileSystem)
-	fs.Root = newDir("/", 0, 0, nil, "", Permanent)
-	fs.Stats = newStats()
-	fs.WatcherHub = newWatchHub(1000, fs.Stats)
+func New() *Store {
+	s := new(Store)
+	s.Root = newDir("/", 0, 0, nil, "", Permanent)
+	s.Stats = newStats()
+	s.WatcherHub = newWatchHub(1000)
 
-	return fs
+	return s
 
 }
 
-func (fs *FileSystem) Get(nodePath string, recursive, sorted bool, index uint64, term uint64) (*Event, error) {
+func (s *Store) Get(nodePath string, recursive, sorted bool, index uint64, term uint64) (*Event, error) {
 	nodePath = path.Clean(path.Join("/", nodePath))
 
-	n, err := fs.InternalGet(nodePath, index, term)
+	n, err := s.InternalGet(nodePath, index, term)
 
 	if err != nil {
-		fs.Stats.IncStats(StatsGetsMiss)
+		s.Stats.Inc(GetFail)
 		return nil, err
 	}
 
@@ -82,61 +82,62 @@ func (fs *FileSystem) Get(nodePath string, recursive, sorted bool, index uint64,
 		e.TTL = int64(n.ExpireTime.Sub(time.Now())/time.Second) + 1
 	}
 
-	fs.Stats.IncStats(StatsGetsHit)
+	s.Stats.Inc(GetSuccess)
+
 	return e, nil
 }
 
 // Create function creates the Node at nodePath. Create will help to create intermediate directories with no ttl.
 // If the node has already existed, create will fail.
 // If any node on the path is a file, create will fail.
-func (fs *FileSystem) Create(nodePath string, value string, expireTime time.Time, index uint64, term uint64) (*Event, error) {
+func (s *Store) Create(nodePath string, value string, expireTime time.Time, index uint64, term uint64) (*Event, error) {
 	nodePath = path.Clean(path.Join("/", nodePath))
 
 	// make sure we can create the node
-	_, err := fs.InternalGet(nodePath, index, term)
+	_, err := s.InternalGet(nodePath, index, term)
 
 	if err == nil { // key already exists
-		fs.Stats.IncStats(StatsSetsMiss)
+		s.Stats.Inc(SetFail)
 		return nil, etcdErr.NewError(etcdErr.EcodeNodeExist, nodePath)
 	}
 
 	etcdError, _ := err.(etcdErr.Error)
 
 	if etcdError.ErrorCode == 104 { // we cannot create the key due to meet a file while walking
-		fs.Stats.IncStats(StatsSetsMiss)
+		s.Stats.Inc(SetFail)
 		return nil, err
 	}
 
 	dir, _ := path.Split(nodePath)
 
 	// walk through the nodePath, create dirs and get the last directory node
-	d, err := fs.walk(dir, fs.checkDir)
+	d, err := s.walk(dir, s.checkDir)
 
 	if err != nil {
-		fs.Stats.IncStats(StatsSetsMiss)
+		s.Stats.Inc(SetFail)
 		return nil, err
 	}
 
-	e := newEvent(Create, nodePath, fs.Index, fs.Term)
+	e := newEvent(Create, nodePath, s.Index, s.Term)
 
 	var n *Node
 
 	if len(value) != 0 { // create file
 		e.Value = value
 
-		n = newFile(nodePath, value, fs.Index, fs.Term, d, "", expireTime)
+		n = newFile(nodePath, value, s.Index, s.Term, d, "", expireTime)
 
 	} else { // create directory
 		e.Dir = true
 
-		n = newDir(nodePath, fs.Index, fs.Term, d, "", expireTime)
+		n = newDir(nodePath, s.Index, s.Term, d, "", expireTime)
 
 	}
 
 	err = d.Add(n)
 
 	if err != nil {
-		fs.Stats.IncStats(StatsSetsMiss)
+		s.Stats.Inc(SetFail)
 		return nil, err
 	}
 
@@ -147,28 +148,28 @@ func (fs *FileSystem) Create(nodePath string, value string, expireTime time.Time
 		e.TTL = int64(expireTime.Sub(time.Now())/time.Second) + 1
 	}
 
-	fs.WatcherHub.notify(e)
-	fs.Stats.IncStats(StatsSetsHit)
+	s.WatcherHub.notify(e)
+	s.Stats.Inc(SetSuccess)
 	return e, nil
 }
 
 // Update function updates the value/ttl of the node.
 // If the node is a file, the value and the ttl can be updated.
 // If the node is a directory, only the ttl can be updated.
-func (fs *FileSystem) Update(nodePath string, value string, expireTime time.Time, index uint64, term uint64) (*Event, error) {
-	n, err := fs.InternalGet(nodePath, index, term)
+func (s *Store) Update(nodePath string, value string, expireTime time.Time, index uint64, term uint64) (*Event, error) {
+	n, err := s.InternalGet(nodePath, index, term)
 
 	if err != nil { // if the node does not exist, return error
-		fs.Stats.IncStats(StatsUpdatesMiss)
+		s.Stats.Inc(UpdateFail)
 		return nil, err
 	}
 
-	e := newEvent(Update, nodePath, fs.Index, fs.Term)
+	e := newEvent(Update, nodePath, s.Index, s.Term)
 
 	if n.IsDir() { // if the node is a directory, we can only update ttl
 
 		if len(value) != 0 {
-			fs.Stats.IncStats(StatsUpdatesMiss)
+			s.Stats.Inc(UpdateFail)
 			return nil, etcdErr.NewError(etcdErr.EcodeNotFile, nodePath)
 		}
 
@@ -194,23 +195,23 @@ func (fs *FileSystem) Update(nodePath string, value string, expireTime time.Time
 		e.TTL = int64(expireTime.Sub(time.Now())/time.Second) + 1
 	}
 
-	fs.WatcherHub.notify(e)
-	fs.Stats.IncStats(StatsUpdatesHit)
+	s.WatcherHub.notify(e)
+	s.Stats.Inc(UpdateSuccess)
 	return e, nil
 }
 
-func (fs *FileSystem) TestAndSet(nodePath string, prevValue string, prevIndex uint64,
+func (s *Store) TestAndSet(nodePath string, prevValue string, prevIndex uint64,
 	value string, expireTime time.Time, index uint64, term uint64) (*Event, error) {
 
-	f, err := fs.InternalGet(nodePath, index, term)
+	f, err := s.InternalGet(nodePath, index, term)
 
 	if err != nil {
-		fs.Stats.IncStats(StatsTestAndSetsMiss)
+		s.Stats.Inc(TestAndSetFail)
 		return nil, err
 	}
 
 	if f.IsDir() { // can only test and set file
-		fs.Stats.IncStats(StatsTestAndSetsMiss)
+		s.Stats.Inc(TestAndSetFail)
 		return nil, etcdErr.NewError(etcdErr.EcodeNotFile, nodePath)
 	}
 
@@ -221,23 +222,23 @@ func (fs *FileSystem) TestAndSet(nodePath string, prevValue string, prevIndex ui
 		e.Value = value
 		f.Write(value, index, term)
 
-		fs.WatcherHub.notify(e)
-		fs.Stats.IncStats(StatsTestAndSetsHit)
+		s.WatcherHub.notify(e)
+		s.Stats.Inc(TestAndSetSuccess)
 		return e, nil
 	}
 
 	cause := fmt.Sprintf("[%v != %v] [%v != %v]", prevValue, f.Value, prevIndex, f.ModifiedIndex)
-	fs.Stats.IncStats(StatsTestAndSetsMiss)
+	s.Stats.Inc(TestAndSetFail)
 	return nil, etcdErr.NewError(etcdErr.EcodeTestFailed, cause)
 }
 
 // Delete function deletes the node at the given path.
 // If the node is a directory, recursive must be true to delete it.
-func (fs *FileSystem) Delete(nodePath string, recursive bool, index uint64, term uint64) (*Event, error) {
-	n, err := fs.InternalGet(nodePath, index, term)
+func (s *Store) Delete(nodePath string, recursive bool, index uint64, term uint64) (*Event, error) {
+	n, err := s.InternalGet(nodePath, index, term)
 
 	if err != nil { // if the node does not exist, return error
-		fs.Stats.IncStats(StatsDeletesMiss)
+		s.Stats.Inc(DeleteFail)
 		return nil, err
 	}
 
@@ -250,37 +251,37 @@ func (fs *FileSystem) Delete(nodePath string, recursive bool, index uint64, term
 	}
 
 	callback := func(path string) { // notify function
-		fs.WatcherHub.notifyWithPath(e, path, true)
+		s.WatcherHub.notifyWithPath(e, path, true)
 	}
 
 	err = n.Remove(recursive, callback)
 
 	if err != nil {
-		fs.Stats.IncStats(StatsDeletesMiss)
+		s.Stats.Inc(DeleteFail)
 		return nil, err
 	}
 
-	fs.WatcherHub.notify(e)
-	fs.Stats.IncStats(StatsDeletesHit)
+	s.WatcherHub.notify(e)
+	s.Stats.Inc(DeleteSuccess)
 
 	return e, nil
 }
 
-func (fs *FileSystem) Watch(prefix string, recursive bool, sinceIndex uint64, index uint64, term uint64) (<-chan *Event, error) {
-	fs.Index, fs.Term = index, term
+func (s *Store) Watch(prefix string, recursive bool, sinceIndex uint64, index uint64, term uint64) (<-chan *Event, error) {
+	s.Index, s.Term = index, term
 
 	if sinceIndex == 0 {
-		return fs.WatcherHub.watch(prefix, recursive, index+1)
+		return s.WatcherHub.watch(prefix, recursive, index+1)
 	}
 
-	return fs.WatcherHub.watch(prefix, recursive, sinceIndex)
+	return s.WatcherHub.watch(prefix, recursive, sinceIndex)
 }
 
 // walk function walks all the nodePath and apply the walkFunc on each directory
-func (fs *FileSystem) walk(nodePath string, walkFunc func(prev *Node, component string) (*Node, error)) (*Node, error) {
+func (s *Store) walk(nodePath string, walkFunc func(prev *Node, component string) (*Node, error)) (*Node, error) {
 	components := strings.Split(nodePath, "/")
 
-	curr := fs.Root
+	curr := s.Root
 
 	var err error
 	for i := 1; i < len(components); i++ {
@@ -299,11 +300,11 @@ func (fs *FileSystem) walk(nodePath string, walkFunc func(prev *Node, component
 }
 
 // InternalGet function get the node of the given nodePath.
-func (fs *FileSystem) InternalGet(nodePath string, index uint64, term uint64) (*Node, error) {
+func (s *Store) InternalGet(nodePath string, index uint64, term uint64) (*Node, error) {
 	nodePath = path.Clean(path.Join("/", nodePath))
 
 	// update file system known index and term
-	fs.Index, fs.Term = index, term
+	s.Index, s.Term = index, term
 
 	walkFunc := func(parent *Node, name string) (*Node, error) {
 
@@ -319,7 +320,7 @@ func (fs *FileSystem) InternalGet(nodePath string, index uint64, term uint64) (*
 		return nil, etcdErr.NewError(etcdErr.EcodeKeyNotFound, path.Join(parent.Path, name))
 	}
 
-	f, err := fs.walk(nodePath, walkFunc)
+	f, err := s.walk(nodePath, walkFunc)
 
 	if err != nil {
 		return nil, err
@@ -332,14 +333,14 @@ func (fs *FileSystem) InternalGet(nodePath string, index uint64, term uint64) (*
 // If it is a directory, this function will return the pointer to that node.
 // If it does not exist, this function will create a new directory and return the pointer to that node.
 // If it is a file, this function will return error.
-func (fs *FileSystem) checkDir(parent *Node, dirName string) (*Node, error) {
+func (s *Store) checkDir(parent *Node, dirName string) (*Node, error) {
 	subDir, ok := parent.Children[dirName]
 
 	if ok {
 		return subDir, nil
 	}
 
-	n := newDir(path.Join(parent.Path, dirName), fs.Index, fs.Term, parent, parent.ACL, Permanent)
+	n := newDir(path.Join(parent.Path, dirName), s.Index, s.Term, parent, parent.ACL, Permanent)
 
 	parent.Children[dirName] = n
 
@@ -350,24 +351,20 @@ func (fs *FileSystem) checkDir(parent *Node, dirName string) (*Node, error) {
 // Save function will not be able to save the state of watchers.
 // Save function will not save the parent field of the node. Or there will
 // be cyclic dependencies issue for the json package.
-func (fs *FileSystem) Save() ([]byte, error) {
+func (s *Store) Save() ([]byte, error) {
+	clonedStore := New()
+	clonedStore.Root = s.Root.Clone()
+	clonedStore.WatcherHub = s.WatcherHub
+	clonedStore.Index = s.Index
+	clonedStore.Term = s.Term
+	clonedStore.Stats = s.Stats
 
-	fs.Stats.IncStats(StatsSaveHit)
-	cloneFs := New()
-	cloneFs.Root = fs.Root.Clone()
-
-	b, err := json.Marshal(fs)
+	b, err := json.Marshal(clonedStore)
 
 	if err != nil {
-		fs.Stats.IncStats(StatsSaveMiss)
-		fs.Stats.rwlock.Lock()
-		fs.Stats.SaveHit-- // restore the savehit
-		fs.Stats.rwlock.Unlock()
-
 		return nil, err
 	}
 
-	fs.Stats.IncStats(StatsSaveHit)
 	return b, nil
 }
 
@@ -375,15 +372,18 @@ func (fs *FileSystem) Save() ([]byte, error) {
 // It needs to recovery the parent field of the nodes.
 // It needs to delete the expired nodes since the saved time and also
 // need to create monitor go routines.
-func (fs *FileSystem) Recovery(state []byte) error {
-	err := json.Unmarshal(state, fs)
+func (s *Store) Recovery(state []byte) error {
+	err := json.Unmarshal(state, s)
 
 	if err != nil {
-		fs.Stats.IncStats(StatsRecoveryMiss)
 		return err
 	}
 
-	fs.Root.recoverAndclean()
-	fs.Stats.IncStats(StatsRecoveryHit)
+	s.Root.recoverAndclean()
 	return nil
 }
+
+func (s *Store) JsonStats() []byte {
+	s.Stats.Watchers = uint64(s.WatcherHub.count)
+	return s.Stats.toJson()
+}
diff --git a/file_system/file_system_test.go b/store/store_test.go
similarity index 68%
rename from file_system/file_system_test.go
rename to store/store_test.go
index 0478f9c30..259310ff4 100644
--- a/file_system/file_system_test.go
+++ b/store/store_test.go
@@ -1,4 +1,4 @@
-package fileSystem
+package store
 
 import (
 	"math/rand"
@@ -8,46 +8,46 @@ import (
 )
 
 func TestCreateAndGet(t *testing.T) {
-	fs := New()
+	s := New()
 
-	fs.Create("/foobar", "bar", Permanent, 1, 1)
+	s.Create("/foobar", "bar", Permanent, 1, 1)
 
 	// already exist, create should fail
-	_, err := fs.Create("/foobar", "bar", Permanent, 1, 1)
+	_, err := s.Create("/foobar", "bar", Permanent, 1, 1)
 
 	if err == nil {
 		t.Fatal("Create should fail")
 	}
 
-	fs.Delete("/foobar", true, 1, 1)
+	s.Delete("/foobar", true, 1, 1)
 
 	// this should create successfully
-	createAndGet(fs, "/foobar", t)
-	createAndGet(fs, "/foo/bar", t)
-	createAndGet(fs, "/foo/foo/bar", t)
+	createAndGet(s, "/foobar", t)
+	createAndGet(s, "/foo/bar", t)
+	createAndGet(s, "/foo/foo/bar", t)
 
 	// meet file, create should fail
-	_, err = fs.Create("/foo/bar/bar", "bar", Permanent, 2, 1)
+	_, err = s.Create("/foo/bar/bar", "bar", Permanent, 2, 1)
 
 	if err == nil {
 		t.Fatal("Create should fail")
 	}
 
 	// create a directory
-	_, err = fs.Create("/fooDir", "", Permanent, 3, 1)
+	_, err = s.Create("/fooDir", "", Permanent, 3, 1)
 
 	if err != nil {
 		t.Fatal("Cannot create /fooDir")
 	}
 
-	e, err := fs.Get("/fooDir", false, false, 3, 1)
+	e, err := s.Get("/fooDir", false, false, 3, 1)
 
 	if err != nil || e.Dir != true {
 		t.Fatal("Cannot create /fooDir ")
 	}
 
 	// create a file under directory
-	_, err = fs.Create("/fooDir/bar", "bar", Permanent, 4, 1)
+	_, err = s.Create("/fooDir/bar", "bar", Permanent, 4, 1)
 
 	if err != nil {
 		t.Fatal("Cannot create /fooDir/bar = bar")
@@ -56,21 +56,21 @@ func TestCreateAndGet(t *testing.T) {
 }
 
 func TestUpdateFile(t *testing.T) {
-	fs := New()
+	s := New()
 
-	_, err := fs.Create("/foo/bar", "bar", Permanent, 1, 1)
+	_, err := s.Create("/foo/bar", "bar", Permanent, 1, 1)
 
 	if err != nil {
 		t.Fatalf("cannot create %s=bar [%s]", "/foo/bar", err.Error())
 	}
 
-	_, err = fs.Update("/foo/bar", "barbar", Permanent, 2, 1)
+	_, err = s.Update("/foo/bar", "barbar", Permanent, 2, 1)
 
 	if err != nil {
 		t.Fatalf("cannot update %s=barbar [%s]", "/foo/bar", err.Error())
 	}
 
-	e, err := fs.Get("/foo/bar", false, false, 2, 1)
+	e, err := s.Get("/foo/bar", false, false, 2, 1)
 
 	if err != nil {
 		t.Fatalf("cannot get %s [%s]", "/foo/bar", err.Error())
@@ -82,37 +82,37 @@ func TestUpdateFile(t *testing.T) {
 
 	// create a directory, update its ttl, to see if it will be deleted
 
-	_, err = fs.Create("/foo/foo", "", Permanent, 3, 1)
+	_, err = s.Create("/foo/foo", "", Permanent, 3, 1)
 
 	if err != nil {
 		t.Fatalf("cannot create dir [%s] [%s]", "/foo/foo", err.Error())
 	}
 
-	_, err = fs.Create("/foo/foo/foo1", "bar1", Permanent, 4, 1)
+	_, err = s.Create("/foo/foo/foo1", "bar1", Permanent, 4, 1)
 
 	if err != nil {
 		t.Fatal("cannot create [%s]", err.Error())
 	}
 
-	_, err = fs.Create("/foo/foo/foo2", "", Permanent, 5, 1)
+	_, err = s.Create("/foo/foo/foo2", "", Permanent, 5, 1)
 	if err != nil {
 		t.Fatal("cannot create [%s]", err.Error())
 	}
 
-	_, err = fs.Create("/foo/foo/foo2/boo", "boo1", Permanent, 6, 1)
+	_, err = s.Create("/foo/foo/foo2/boo", "boo1", Permanent, 6, 1)
 	if err != nil {
 		t.Fatal("cannot create [%s]", err.Error())
 	}
 
 	expire := time.Now().Add(time.Second * 2)
-	_, err = fs.Update("/foo/foo", "", expire, 7, 1)
+	_, err = s.Update("/foo/foo", "", expire, 7, 1)
 	if err != nil {
 		t.Fatalf("cannot update dir [%s] [%s]", "/foo/foo", err.Error())
 	}
 
 	// sleep 50ms, it should still reach the node
 	time.Sleep(time.Microsecond * 50)
-	e, err = fs.Get("/foo/foo", true, false, 7, 1)
+	e, err = s.Get("/foo/foo", true, false, 7, 1)
 
 	if err != nil || e.Key != "/foo/foo" {
 		t.Fatalf("cannot get dir before expiration [%s]", err.Error())
@@ -132,23 +132,23 @@ func TestUpdateFile(t *testing.T) {
 
 	// wait for expiration
 	time.Sleep(time.Second * 3)
-	e, err = fs.Get("/foo/foo", true, false, 7, 1)
+	e, err = s.Get("/foo/foo", true, false, 7, 1)
 
 	if err == nil {
 		t.Fatal("still can get dir after expiration [%s]")
 	}
 
-	_, err = fs.Get("/foo/foo/foo1", true, false, 7, 1)
+	_, err = s.Get("/foo/foo/foo1", true, false, 7, 1)
 	if err == nil {
 		t.Fatal("still can get sub node after expiration [%s]")
 	}
 
-	_, err = fs.Get("/foo/foo/foo2", true, false, 7, 1)
+	_, err = s.Get("/foo/foo/foo2", true, false, 7, 1)
 	if err == nil {
 		t.Fatal("still can get sub dir after expiration [%s]")
 	}
 
-	_, err = fs.Get("/foo/foo/foo2/boo", true, false, 7, 1)
+	_, err = s.Get("/foo/foo/foo2/boo", true, false, 7, 1)
 	if err == nil {
 		t.Fatalf("still can get sub node of sub dir after expiration [%s]", err.Error())
 	}
@@ -156,17 +156,17 @@ func TestUpdateFile(t *testing.T) {
 }
 
 func TestListDirectory(t *testing.T) {
-	fs := New()
+	s := New()
 
 	// create dir /foo
 	// set key-value /foo/foo=bar
-	fs.Create("/foo/foo", "bar", Permanent, 1, 1)
+	s.Create("/foo/foo", "bar", Permanent, 1, 1)
 
 	// create dir /foo/fooDir
 	// set key-value /foo/fooDir/foo=bar
-	fs.Create("/foo/fooDir/foo", "bar", Permanent, 2, 1)
+	s.Create("/foo/fooDir/foo", "bar", Permanent, 2, 1)
 
-	e, err := fs.Get("/foo", true, false, 2, 1)
+	e, err := s.Get("/foo", true, false, 2, 1)
 
 	if err != nil {
 		t.Fatalf("%v", err)
@@ -191,9 +191,9 @@ func TestListDirectory(t *testing.T) {
 
 	// create dir /foo/_hidden
 	// set key-value /foo/_hidden/foo -> bar
-	fs.Create("/foo/_hidden/foo", "bar", Permanent, 3, 1)
+	s.Create("/foo/_hidden/foo", "bar", Permanent, 3, 1)
 
-	e, _ = fs.Get("/foo", false, false, 2, 1)
+	e, _ = s.Get("/foo", false, false, 2, 1)
 
 	if len(e.KVPairs) != 2 {
 		t.Fatalf("hidden node is not hidden! %s", e.KVPairs[2].Key)
@@ -201,38 +201,38 @@ func TestListDirectory(t *testing.T) {
 }
 
 func TestRemove(t *testing.T) {
-	fs := New()
+	s := New()
 
-	fs.Create("/foo", "bar", Permanent, 1, 1)
-	_, err := fs.Delete("/foo", false, 1, 1)
+	s.Create("/foo", "bar", Permanent, 1, 1)
+	_, err := s.Delete("/foo", false, 1, 1)
 
 	if err != nil {
 		t.Fatalf("cannot delete %s [%s]", "/foo", err.Error())
 	}
 
-	_, err = fs.Get("/foo", false, false, 1, 1)
+	_, err = s.Get("/foo", false, false, 1, 1)
 
 	if err == nil || err.Error() != "Key Not Found" {
 		t.Fatalf("can get the node after deletion")
 	}
 
-	fs.Create("/foo/bar", "bar", Permanent, 1, 1)
-	fs.Create("/foo/car", "car", Permanent, 1, 1)
-	fs.Create("/foo/dar/dar", "dar", Permanent, 1, 1)
+	s.Create("/foo/bar", "bar", Permanent, 1, 1)
+	s.Create("/foo/car", "car", Permanent, 1, 1)
+	s.Create("/foo/dar/dar", "dar", Permanent, 1, 1)
 
-	_, err = fs.Delete("/foo", false, 1, 1)
+	_, err = s.Delete("/foo", false, 1, 1)
 
 	if err == nil {
 		t.Fatalf("should not be able to delete a directory without recursive")
 	}
 
-	_, err = fs.Delete("/foo", true, 1, 1)
+	_, err = s.Delete("/foo", true, 1, 1)
 
 	if err != nil {
 		t.Fatalf("cannot delete %s [%s]", "/foo", err.Error())
 	}
 
-	_, err = fs.Get("/foo", false, false, 1, 1)
+	_, err = s.Get("/foo", false, false, 1, 1)
 
 	if err == nil || err.Error() != "Key Not Found" {
 		t.Fatalf("can get the node after deletion ")
@@ -241,13 +241,13 @@ func TestRemove(t *testing.T) {
 }
 
 func TestExpire(t *testing.T) {
-	fs := New()
+	s := New()
 
 	expire := time.Now().Add(time.Second)
 
-	fs.Create("/foo", "bar", expire, 1, 1)
+	s.Create("/foo", "bar", expire, 1, 1)
 
-	_, err := fs.InternalGet("/foo", 1, 1)
+	_, err := s.InternalGet("/foo", 1, 1)
 
 	if err != nil {
 		t.Fatalf("can not get the node")
@@ -255,7 +255,7 @@ func TestExpire(t *testing.T) {
 
 	time.Sleep(time.Second * 2)
 
-	_, err = fs.InternalGet("/foo", 1, 1)
+	_, err = s.InternalGet("/foo", 1, 1)
 
 	if err == nil {
 		t.Fatalf("can get the node after expiration time")
@@ -263,10 +263,10 @@ func TestExpire(t *testing.T) {
 
 	// test if we can reach the node before expiration
 	expire = time.Now().Add(time.Second)
-	fs.Create("/foo", "bar", expire, 1, 1)
+	s.Create("/foo", "bar", expire, 1, 1)
 
 	time.Sleep(time.Millisecond * 50)
-	_, err = fs.InternalGet("/foo", 1, 1)
+	_, err = s.InternalGet("/foo", 1, 1)
 
 	if err != nil {
 		t.Fatalf("cannot get the node before expiration", err.Error())
@@ -274,8 +274,8 @@ func TestExpire(t *testing.T) {
 
 	expire = time.Now().Add(time.Second)
 
-	fs.Create("/foo", "bar", expire, 1, 1)
-	_, err = fs.Delete("/foo", false, 1, 1)
+	s.Create("/foo", "bar", expire, 1, 1)
+	_, err = s.Delete("/foo", false, 1, 1)
 
 	if err != nil {
 		t.Fatalf("cannot delete the node before expiration", err.Error())
@@ -284,17 +284,17 @@ func TestExpire(t *testing.T) {
 }
 
 func TestTestAndSet(t *testing.T) { // TODO prevValue == nil ?
-	fs := New()
-	fs.Create("/foo", "bar", Permanent, 1, 1)
+	s := New()
+	s.Create("/foo", "bar", Permanent, 1, 1)
 
 	// test on wrong previous value
-	_, err := fs.TestAndSet("/foo", "barbar", 0, "car", Permanent, 2, 1)
+	_, err := s.TestAndSet("/foo", "barbar", 0, "car", Permanent, 2, 1)
 	if err == nil {
 		t.Fatal("test and set should fail barbar != bar")
 	}
 
 	// test on value
-	e, err := fs.TestAndSet("/foo", "bar", 0, "car", Permanent, 3, 1)
+	e, err := s.TestAndSet("/foo", "bar", 0, "car", Permanent, 3, 1)
 
 	if err != nil {
 		t.Fatal("test and set should succeed bar == bar")
@@ -305,7 +305,7 @@ func TestTestAndSet(t *testing.T) { // TODO prevValue == nil ?
 	}
 
 	// test on index
-	e, err = fs.TestAndSet("/foo", "", 3, "bar", Permanent, 4, 1)
+	e, err = s.TestAndSet("/foo", "", 3, "bar", Permanent, 4, 1)
 
 	if err != nil {
 		t.Fatal("test and set should succeed index 3 == 3")
@@ -318,61 +318,61 @@ func TestTestAndSet(t *testing.T) { // TODO prevValue == nil ?
 }
 
 func TestWatch(t *testing.T) {
-	fs := New()
+	s := New()
 	// watch at a deeper path
-	c, _ := fs.WatcherHub.watch("/foo/foo/foo", false, 0)
-	fs.Create("/foo/foo/foo", "bar", Permanent, 1, 1)
+	c, _ := s.WatcherHub.watch("/foo/foo/foo", false, 0)
+	s.Create("/foo/foo/foo", "bar", Permanent, 1, 1)
 
 	e := nonblockingRetrive(c)
 	if e.Key != "/foo/foo/foo" {
 		t.Fatal("watch for Create node fails")
 	}
 
-	c, _ = fs.WatcherHub.watch("/foo/foo/foo", false, 0)
-	fs.Update("/foo/foo/foo", "car", Permanent, 2, 1)
+	c, _ = s.WatcherHub.watch("/foo/foo/foo", false, 0)
+	s.Update("/foo/foo/foo", "car", Permanent, 2, 1)
 	e = nonblockingRetrive(c)
 	if e.Key != "/foo/foo/foo" {
 		t.Fatal("watch for Update node fails")
 	}
 
-	c, _ = fs.WatcherHub.watch("/foo/foo/foo", false, 0)
-	fs.TestAndSet("/foo/foo/foo", "car", 0, "bar", Permanent, 3, 1)
+	c, _ = s.WatcherHub.watch("/foo/foo/foo", false, 0)
+	s.TestAndSet("/foo/foo/foo", "car", 0, "bar", Permanent, 3, 1)
 	e = nonblockingRetrive(c)
 	if e.Key != "/foo/foo/foo" {
 		t.Fatal("watch for TestAndSet node fails")
 	}
 
-	c, _ = fs.WatcherHub.watch("/foo/foo/foo", false, 0)
-	fs.Delete("/foo", true, 4, 1) //recursively delete
+	c, _ = s.WatcherHub.watch("/foo/foo/foo", false, 0)
+	s.Delete("/foo", true, 4, 1) //recursively delete
 	e = nonblockingRetrive(c)
 	if e.Key != "/foo" {
 		t.Fatal("watch for Delete node fails")
 	}
 
 	// watch at a prefix
-	c, _ = fs.WatcherHub.watch("/foo", true, 0)
-	fs.Create("/foo/foo/boo", "bar", Permanent, 5, 1)
+	c, _ = s.WatcherHub.watch("/foo", true, 0)
+	s.Create("/foo/foo/boo", "bar", Permanent, 5, 1)
 	e = nonblockingRetrive(c)
 	if e.Key != "/foo/foo/boo" {
 		t.Fatal("watch for Create subdirectory fails")
 	}
 
-	c, _ = fs.WatcherHub.watch("/foo", true, 0)
-	fs.Update("/foo/foo/boo", "foo", Permanent, 6, 1)
+	c, _ = s.WatcherHub.watch("/foo", true, 0)
+	s.Update("/foo/foo/boo", "foo", Permanent, 6, 1)
 	e = nonblockingRetrive(c)
 	if e.Key != "/foo/foo/boo" {
 		t.Fatal("watch for Update subdirectory fails")
 	}
 
-	c, _ = fs.WatcherHub.watch("/foo", true, 0)
-	fs.TestAndSet("/foo/foo/boo", "foo", 0, "bar", Permanent, 7, 1)
+	c, _ = s.WatcherHub.watch("/foo", true, 0)
+	s.TestAndSet("/foo/foo/boo", "foo", 0, "bar", Permanent, 7, 1)
 	e = nonblockingRetrive(c)
 	if e.Key != "/foo/foo/boo" {
 		t.Fatal("watch for TestAndSet subdirectory fails")
 	}
 
-	c, _ = fs.WatcherHub.watch("/foo", true, 0)
-	fs.Delete("/foo/foo/boo", false, 8, 1)
+	c, _ = s.WatcherHub.watch("/foo", true, 0)
+	s.Delete("/foo/foo/boo", false, 8, 1)
 	e = nonblockingRetrive(c)
 	if e.Key != "/foo/foo/boo" {
 		t.Fatal("watch for Delete subdirectory fails")
@@ -381,14 +381,14 @@ func TestWatch(t *testing.T) {
 }
 
 func TestSort(t *testing.T) {
-	fs := New()
+	s := New()
 
 	// simulating random creation
 	keys := GenKeys(80, 4)
 
 	i := uint64(1)
 	for _, k := range keys {
-		_, err := fs.Create(k, "bar", Permanent, i, 1)
+		_, err := s.Create(k, "bar", Permanent, i, 1)
 		if err != nil {
 			panic(err)
 		} else {
@@ -396,7 +396,7 @@ func TestSort(t *testing.T) {
 		}
 	}
 
-	e, err := fs.Get("/foo", true, true, i, 1)
+	e, err := s.Get("/foo", true, true, i, 1)
 	if err != nil {
 		t.Fatalf("get dir nodes failed [%s]", err.Error())
 	}
@@ -419,14 +419,14 @@ func TestSort(t *testing.T) {
 }
 
 func TestSaveAndRecover(t *testing.T) {
-	fs := New()
+	s := New()
 
 	// simulating random creation
 	keys := GenKeys(8, 4)
 
 	i := uint64(1)
 	for _, k := range keys {
-		_, err := fs.Create(k, "bar", Permanent, i, 1)
+		_, err := s.Create(k, "bar", Permanent, i, 1)
 		if err != nil {
 			panic(err)
 		} else {
@@ -438,8 +438,8 @@ func TestSaveAndRecover(t *testing.T) {
 	// test if we can reach the node before expiration
 
 	expire := time.Now().Add(time.Second)
-	fs.Create("/foo/foo", "bar", expire, 1, 1)
-	b, err := fs.Save()
+	s.Create("/foo/foo", "bar", expire, 1, 1)
+	b, err := s.Save()
 
 	cloneFs := New()
 	time.Sleep(time.Second)
@@ -453,18 +453,18 @@ func TestSaveAndRecover(t *testing.T) {
 		}
 	}
 
-	if fs.WatcherHub.EventHistory.StartIndex != cloneFs.WatcherHub.EventHistory.StartIndex {
+	if s.WatcherHub.EventHistory.StartIndex != cloneFs.WatcherHub.EventHistory.StartIndex {
 		t.Fatal("Error recovered event history start index")
 	}
 
-	for i = 0; int(i) < fs.WatcherHub.EventHistory.Queue.Size; i++ {
-		if fs.WatcherHub.EventHistory.Queue.Events[i].Key !=
+	for i = 0; int(i) < s.WatcherHub.EventHistory.Queue.Size; i++ {
+		if s.WatcherHub.EventHistory.Queue.Events[i].Key !=
 			cloneFs.WatcherHub.EventHistory.Queue.Events[i].Key {
 			t.Fatal("Error recovered event history")
 		}
 	}
 
-	_, err = fs.Get("/foo/foo", false, false, 1, 1)
+	_, err = s.Get("/foo/foo", false, false, 1, 1)
 
 	if err == nil || err.Error() != "Key Not Found" {
 		t.Fatalf("can get the node after deletion ")
@@ -488,14 +488,14 @@ func GenKeys(num int, depth int) []string {
 	return keys
 }
 
-func createAndGet(fs *FileSystem, path string, t *testing.T) {
-	_, err := fs.Create(path, "bar", Permanent, 1, 1)
+func createAndGet(s *Store, path string, t *testing.T) {
+	_, err := s.Create(path, "bar", Permanent, 1, 1)
 
 	if err != nil {
 		t.Fatalf("cannot create %s=bar [%s]", path, err.Error())
 	}
 
-	e, err := fs.Get(path, false, false, 1, 1)
+	e, err := s.Get(path, false, false, 1, 1)
 
 	if err != nil {
 		t.Fatalf("cannot get %s [%s]", path, err.Error())
diff --git a/file_system/watcher.go b/store/watcher.go
similarity index 84%
rename from file_system/watcher.go
rename to store/watcher.go
index 30fc89da7..1e946e3c0 100644
--- a/file_system/watcher.go
+++ b/store/watcher.go
@@ -1,16 +1,16 @@
-package fileSystem
+package store
 
 import (
 	"container/list"
 	"path"
 	"strings"
+	"sync/atomic"
 )
 
 type watcherHub struct {
 	watchers     map[string]*list.List
-	count        uint64 // current number of watchers
+	count        int64 // current number of watchers.
 	EventHistory *EventHistory
-	Stats        *EtcdStats
 }
 
 type watcher struct {
@@ -19,11 +19,10 @@ type watcher struct {
 	sinceIndex uint64
 }
 
-func newWatchHub(capacity int, stats *EtcdStats) *watcherHub {
+func newWatchHub(capacity int) *watcherHub {
 	return &watcherHub{
 		watchers:     make(map[string]*list.List),
 		EventHistory: newEventHistory(capacity),
-		Stats:        stats,
 	}
 }
 
@@ -37,13 +36,9 @@ func (wh *watcherHub) watch(prefix string, recursive bool, index uint64) (<-chan
 	e, err := wh.EventHistory.scan(prefix, index)
 
 	if err != nil {
-		wh.Stats.IncStats(StatsWatchMiss)
 		return nil, err
 	}
 
-	wh.Stats.IncStats(StatsWatchHit)
-	wh.Stats.IncStats(StatsInWatchingNum)
-
 	if e != nil {
 		eventChan <- e
 		return eventChan, nil
@@ -66,6 +61,8 @@ func (wh *watcherHub) watch(prefix string, recursive bool, index uint64) (<-chan
 		wh.watchers[prefix] = l
 	}
 
+	atomic.AddInt64(&wh.count, 1)
+
 	return eventChan, nil
 }
 
@@ -94,10 +91,8 @@ func (wh *watcherHub) notifyWithPath(e *Event, path string, force bool) {
 
 			if (w.recursive || force || e.Key == path) && e.Index >= w.sinceIndex {
 				w.eventChan <- e
-				wh.Stats.rwlock.Lock() // lock the InWatchingNum
-				wh.Stats.InWatchingNum--
-				wh.Stats.rwlock.Unlock()
 				l.Remove(curr)
+				atomic.AddInt64(&wh.count, -1)
 			} else {
 				notifiedAll = false
 			}
diff --git a/file_system/watcher_test.go b/store/watcher_test.go
similarity index 92%
rename from file_system/watcher_test.go
rename to store/watcher_test.go
index 132f367f3..90c23c59e 100644
--- a/file_system/watcher_test.go
+++ b/store/watcher_test.go
@@ -1,12 +1,12 @@
-package fileSystem
+package store
 
 import (
 	"testing"
 )
 
 func TestWatcher(t *testing.T) {
-	fs := New()
-	wh := fs.WatcherHub
+	s := New()
+	wh := s.WatcherHub
 	c, err := wh.watch("/foo", true, 0)
 
 	if err != nil {
diff --git a/util.go b/util.go
index 960d12f4a..434de1a24 100644
--- a/util.go
+++ b/util.go
@@ -15,7 +15,7 @@ import (
 	"time"
 
 	etcdErr "github.com/coreos/etcd/error"
-	"github.com/coreos/etcd/file_system"
+	"github.com/coreos/etcd/store"
 	"github.com/coreos/etcd/web"
 	"github.com/coreos/go-raft"
 )
@@ -30,12 +30,12 @@ func durationToExpireTime(strDuration string) (time.Time, error) {
 		duration, err := strconv.Atoi(strDuration)
 
 		if err != nil {
-			return fileSystem.Permanent, err
+			return store.Permanent, err
 		}
 		return time.Now().Add(time.Second * (time.Duration)(duration)), nil
 
 	} else {
-		return fileSystem.Permanent, nil
+		return store.Permanent, nil
 	}
 }