diff --git a/etcdserver/etcdhttp/http.go b/etcdserver/etcdhttp/http.go
index d3135540d..970569d3a 100644
--- a/etcdserver/etcdhttp/http.go
+++ b/etcdserver/etcdhttp/http.go
@@ -1,11 +1,9 @@
 package etcdhttp
 
 import (
-	"encoding/binary"
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io"
 	"io/ioutil"
 	"log"
 	"net/http"
@@ -14,8 +12,6 @@ import (
 	"strings"
 	"time"
 
-	crand "crypto/rand"
-
 	"github.com/coreos/etcd/elog"
 	etcdErr "github.com/coreos/etcd/error"
 	"github.com/coreos/etcd/etcdserver"
@@ -71,7 +67,7 @@ func (h serverHandler) serveKeys(w http.ResponseWriter, r *http.Request) {
 	ctx, cancel := context.WithTimeout(context.Background(), h.timeout)
 	defer cancel()
 
-	rr, err := parseRequest(r, genID())
+	rr, err := parseRequest(r, etcdserver.GenID())
 	if err != nil {
 		writeError(w, err)
 		return
@@ -139,20 +135,6 @@ func (h serverHandler) serveRaft(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusNoContent)
 }
 
-// genID generates a random id that is: n < 0 < n.
-func genID() int64 {
-	for {
-		b := make([]byte, 8)
-		if _, err := io.ReadFull(crand.Reader, b); err != nil {
-			panic(err) // really bad stuff happened
-		}
-		n := int64(binary.BigEndian.Uint64(b))
-		if n != 0 {
-			return n
-		}
-	}
-}
-
 // parseRequest converts a received http.Request to a server Request,
 // performing validation of supplied fields as appropriate.
 // If any validation fails, an empty Request and non-nil error is returned.
diff --git a/etcdserver/etcdserverpb/etcdserver.pb.go b/etcdserver/etcdserverpb/etcdserver.pb.go
index fd9ad85c7..280c85c66 100644
--- a/etcdserver/etcdserverpb/etcdserver.pb.go
+++ b/etcdserver/etcdserverpb/etcdserver.pb.go
@@ -42,6 +42,7 @@ type Request struct {
 	Recursive        bool   `protobuf:"varint,12,req,name=recursive" json:"recursive"`
 	Sorted           bool   `protobuf:"varint,13,req,name=sorted" json:"sorted"`
 	Quorum           bool   `protobuf:"varint,14,req,name=quorum" json:"quorum"`
+	Time             int64  `protobuf:"varint,15,req,name=time" json:"time"`
 	XXX_unrecognized []byte `json:"-"`
 }
 
@@ -321,6 +322,21 @@ func (m *Request) Unmarshal(data []byte) error {
 				}
 			}
 			m.Quorum = bool(v != 0)
+		case 15:
+			if wireType != 0 {
+				return code_google_com_p_gogoprotobuf_proto.ErrWrongType
+			}
+			for shift := uint(0); ; shift += 7 {
+				if index >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[index]
+				index++
+				m.Time |= (int64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
 		default:
 			var sizeOfWire int
 			for {
@@ -367,6 +383,7 @@ func (m *Request) Size() (n int) {
 	n += 2
 	n += 2
 	n += 2
+	n += 1 + sovEtcdserver(uint64(m.Time))
 	if m.XXX_unrecognized != nil {
 		n += len(m.XXX_unrecognized)
 	}
@@ -479,6 +496,9 @@ func (m *Request) MarshalTo(data []byte) (n int, err error) {
 		data[i] = 0
 	}
 	i++
+	data[i] = 0x78
+	i++
+	i = encodeVarintEtcdserver(data, i, uint64(m.Time))
 	if m.XXX_unrecognized != nil {
 		i += copy(data[i:], m.XXX_unrecognized)
 	}
diff --git a/etcdserver/etcdserverpb/etcdserver.proto b/etcdserver/etcdserverpb/etcdserver.proto
index 6031a8983..9cab32874 100644
--- a/etcdserver/etcdserverpb/etcdserver.proto
+++ b/etcdserver/etcdserverpb/etcdserver.proto
@@ -8,18 +8,19 @@ option (gogoproto.unmarshaler_all) = true;
 option (gogoproto.goproto_getters_all) = false;
 
 message Request {
-	required int64  id         =  1 [(gogoproto.nullable) = false];     
+	required int64  id         =  1 [(gogoproto.nullable) = false];
 	required string method     =  2 [(gogoproto.nullable) = false];
 	required string path       =  3 [(gogoproto.nullable) = false];
 	required string val        =  4 [(gogoproto.nullable) = false];
 	required bool   dir        =  5 [(gogoproto.nullable) = false];
 	required string prevValue  =  6 [(gogoproto.nullable) = false];
-	required uint64  prevIndex  =  7 [(gogoproto.nullable) = false];
+	required uint64  prevIndex =  7 [(gogoproto.nullable) = false];
 	required bool   prevExists =  8 [(gogoproto.nullable) = true];
 	required int64  expiration =  9 [(gogoproto.nullable) = false];
 	required bool   wait       = 10 [(gogoproto.nullable) = false];
-	required uint64  since      = 11 [(gogoproto.nullable) = false];
+	required uint64  since     = 11 [(gogoproto.nullable) = false];
 	required bool   recursive  = 12 [(gogoproto.nullable) = false];
 	required bool   sorted     = 13 [(gogoproto.nullable) = false];
 	required bool   quorum     = 14 [(gogoproto.nullable) = false];
+	required int64  time       = 15 [(gogoproto.nullable) = false];
 }
diff --git a/etcdserver/etcdserverpb/genproto.sh b/etcdserver/etcdserverpb/genproto.sh
old mode 100644
new mode 100755
diff --git a/etcdserver/server.go b/etcdserver/server.go
index 12e94b9eb..d60ce9933 100644
--- a/etcdserver/server.go
+++ b/etcdserver/server.go
@@ -1,9 +1,14 @@
 package etcdserver
 
 import (
+	"encoding/binary"
 	"errors"
+	"io"
+	"log"
 	"time"
 
+	crand "crypto/rand"
+
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/raft"
 	"github.com/coreos/etcd/raft/raftpb"
@@ -12,13 +17,15 @@ import (
 	"github.com/coreos/etcd/wait"
 )
 
+const defaultSyncTimeout = time.Second
+
 var (
 	ErrUnknownMethod = errors.New("etcdserver: unknown method")
 	ErrStopped       = errors.New("etcdserver: server stopped")
 )
 
 type SendFunc func(m []raftpb.Message)
-type SaveFunc func(st raftpb.State, ents []raftpb.Entry)
+type SaveFunc func(st raftpb.HardState, ents []raftpb.Entry)
 
 type Response struct {
 	Event   *store.Event
@@ -59,9 +66,10 @@ type EtcdServer struct {
 	// Save specifies the save function for saving ents to stable storage.
 	// Save MUST block until st and ents are on stable storage.  If Send is
 	// nil, server will panic.
-	Save func(st raftpb.State, ents []raftpb.Entry)
+	Save func(st raftpb.HardState, ents []raftpb.Entry)
 
-	Ticker <-chan time.Time
+	Ticker     <-chan time.Time
+	SyncTicker <-chan time.Time
 }
 
 // Start prepares and starts server in a new goroutine. It is no longer safe to
@@ -77,12 +85,13 @@ func (s *EtcdServer) Process(ctx context.Context, m raftpb.Message) error {
 }
 
 func (s *EtcdServer) run() {
+	var syncC <-chan time.Time
 	for {
 		select {
 		case <-s.Ticker:
 			s.Node.Tick()
 		case rd := <-s.Node.Ready():
-			s.Save(rd.State, rd.Entries)
+			s.Save(rd.HardState, rd.Entries)
 			s.Send(rd.Messages)
 
 			// TODO(bmizerany): do this in the background, but take
@@ -95,6 +104,16 @@ func (s *EtcdServer) run() {
 				}
 				s.w.Trigger(r.Id, s.apply(r))
 			}
+
+			if rd.SoftState != nil {
+				if rd.RaftState == raft.StateLeader {
+					syncC = s.SyncTicker
+				} else {
+					syncC = nil
+				}
+			}
+		case <-syncC:
+			s.sync(defaultSyncTimeout)
 		case <-s.done:
 			return
 		}
@@ -109,7 +128,7 @@ func (s *EtcdServer) Stop() {
 }
 
 // Do interprets r and performs an operation on s.Store according to r.Method
-// and other fields. If r.Method is "POST", "PUT", "DELETE", or a "GET with
+// and other fields. If r.Method is "POST", "PUT", "DELETE", or a "GET" with
 // Quorum == true, r will be sent through consensus before performing its
 // respective operation. Do will block until an action is performed or there is
 // an error.
@@ -158,6 +177,29 @@ func (s *EtcdServer) Do(ctx context.Context, r pb.Request) (Response, error) {
 	}
 }
 
+// sync proposes a SYNC request and is non-blocking.
+// This makes no guarantee that the request will be proposed or performed.
+// The request will be cancelled after the given timeout.
+func (s *EtcdServer) sync(timeout time.Duration) {
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	req := pb.Request{
+		Method: "SYNC",
+		Id:     GenID(),
+		Time:   time.Now().UnixNano(),
+	}
+	data, err := req.Marshal()
+	if err != nil {
+		log.Printf("marshal request %#v error: %v", req, err)
+		return
+	}
+	// There is no promise that node has leader when do SYNC request,
+	// so it uses goroutine to propose.
+	go func() {
+		s.Node.Propose(ctx, data)
+		cancel()
+	}()
+}
+
 // apply interprets r as a call to store.X and returns an Response interpreted from store.Event
 func (s *EtcdServer) apply(r pb.Request) Response {
 	f := func(ev *store.Event, err error) Response {
@@ -190,12 +232,30 @@ func (s *EtcdServer) apply(r pb.Request) Response {
 		}
 	case "QGET":
 		return f(s.Store.Get(r.Path, r.Recursive, r.Sorted))
+	case "SYNC":
+		s.Store.DeleteExpiredKeys(time.Unix(0, r.Time))
+		return Response{}
 	default:
 		// This should never be reached, but just in case:
 		return Response{err: ErrUnknownMethod}
 	}
 }
 
+// TODO: move the function to /id pkg maybe?
+// GenID generates a random id that is not equal to 0.
+func GenID() int64 {
+	for {
+		b := make([]byte, 8)
+		if _, err := io.ReadFull(crand.Reader, b); err != nil {
+			panic(err) // really bad stuff happened
+		}
+		n := int64(binary.BigEndian.Uint64(b))
+		if n != 0 {
+			return n
+		}
+	}
+}
+
 func getBool(v *bool) (vv bool, set bool) {
 	if v == nil {
 		return false, false
diff --git a/etcdserver/server_test.go b/etcdserver/server_test.go
index 190fb1b0d..41b32505c 100644
--- a/etcdserver/server_test.go
+++ b/etcdserver/server_test.go
@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"math/rand"
 	"reflect"
+	"runtime"
+	"sync"
 	"testing"
 	"time"
 
@@ -109,6 +111,10 @@ func TestApply(t *testing.T) {
 			pb.Request{Method: "QGET", Id: 1},
 			Response{Event: &store.Event{}}, []string{"Get"},
 		},
+		{
+			pb.Request{Method: "SYNC", Id: 1},
+			Response{}, []string{"DeleteExpiredKeys"},
+		},
 		{
 			pb.Request{Method: "BADMETHOD", Id: 1},
 			Response{err: ErrUnknownMethod}, nil,
@@ -159,7 +165,7 @@ func testServer(t *testing.T, ns int64) {
 			Node:   n,
 			Store:  store.New(),
 			Send:   send,
-			Save:   func(_ raftpb.State, _ []raftpb.Entry) {},
+			Save:   func(_ raftpb.HardState, _ []raftpb.Entry) {},
 			Ticker: tk.C,
 		}
 		srv.Start()
@@ -228,7 +234,7 @@ func TestDoProposal(t *testing.T) {
 			Node:   n,
 			Store:  st,
 			Send:   func(_ []raftpb.Message) {},
-			Save:   func(_ raftpb.State, _ []raftpb.Entry) {},
+			Save:   func(_ raftpb.HardState, _ []raftpb.Entry) {},
 			Ticker: tk,
 		}
 		srv.Start()
@@ -296,7 +302,7 @@ func TestDoProposalStopped(t *testing.T) {
 		Node:   n,
 		Store:  st,
 		Send:   func(_ []raftpb.Message) {},
-		Save:   func(_ raftpb.State, _ []raftpb.Entry) {},
+		Save:   func(_ raftpb.HardState, _ []raftpb.Entry) {},
 		Ticker: tk,
 	}
 	srv.Start()
@@ -318,6 +324,117 @@ func TestDoProposalStopped(t *testing.T) {
 	}
 }
 
+// TestSync tests sync 1. is nonblocking 2. sends out SYNC request.
+func TestSync(t *testing.T) {
+	n := raft.Start(0xBAD0, []int64{0xBAD0}, 10, 1)
+	n.Campaign(context.TODO())
+	select {
+	case <-n.Ready():
+	case <-time.After(time.Millisecond):
+		t.Fatalf("expect to receive ready within 1ms, but fail")
+	}
+
+	srv := &EtcdServer{
+		// TODO: use fake node for better testability
+		Node: n,
+	}
+	start := time.Now()
+	srv.sync(defaultSyncTimeout)
+
+	// check that sync is non-blocking
+	if d := time.Since(start); d > time.Millisecond {
+		t.Errorf("CallSyncTime = %v, want < %v", d, time.Millisecond)
+	}
+
+	// give time for goroutine in sync to run
+	// TODO: use fake clock
+	var ready raft.Ready
+	select {
+	case ready = <-n.Ready():
+	case <-time.After(time.Millisecond):
+		t.Fatalf("expect to receive ready within 1ms, but fail")
+	}
+
+	if len(ready.CommittedEntries) != 1 {
+		t.Fatalf("len(CommittedEntries) = %d, want 1", len(ready.CommittedEntries))
+	}
+	e := ready.CommittedEntries[0]
+	var req pb.Request
+	if err := req.Unmarshal(e.Data); err != nil {
+		t.Fatalf("unmarshal error: %v", err)
+	}
+	if req.Method != "SYNC" {
+		t.Errorf("method = %s, want SYNC", req.Method)
+	}
+}
+
+// TestSyncFail tests the case that sync 1. is non-blocking 2. fails to
+// propose SYNC request because there is no leader
+func TestSyncFail(t *testing.T) {
+	// The node is run without Tick and Campaign, so it has no leader forever.
+	n := raft.Start(0xBAD0, []int64{0xBAD0}, 10, 1)
+	select {
+	case <-n.Ready():
+	case <-time.After(time.Millisecond):
+		t.Fatalf("no ready")
+	}
+
+	srv := &EtcdServer{
+		// TODO: use fake node for better testability
+		Node: n,
+	}
+	routineN := runtime.NumGoroutine()
+	start := time.Now()
+	srv.sync(time.Millisecond)
+
+	// check that sync is non-blocking
+	if d := time.Since(start); d > time.Millisecond {
+		t.Errorf("CallSyncTime = %v, want < %v", d, time.Millisecond)
+	}
+
+	// give time for goroutine in sync to cancel
+	// TODO: use fake clock
+	time.Sleep(2 * time.Millisecond)
+	if g := runtime.NumGoroutine(); g != routineN {
+		t.Errorf("NumGoroutine = %d, want %d", g, routineN)
+	}
+	select {
+	case g := <-n.Ready():
+		t.Errorf("ready = %+v, want no", g)
+	default:
+	}
+}
+
+func TestSyncTriggerDeleteExpriedKeys(t *testing.T) {
+	n := raft.Start(0xBAD0, []int64{0xBAD0}, 10, 1)
+	n.Campaign(context.TODO())
+	st := &storeRecorder{}
+	syncInterval := 5 * time.Millisecond
+	syncTicker := time.NewTicker(syncInterval)
+	defer syncTicker.Stop()
+	srv := &EtcdServer{
+		// TODO: use fake node for better testability
+		Node:       n,
+		Store:      st,
+		Send:       func(_ []raftpb.Message) {},
+		Save:       func(_ raftpb.HardState, _ []raftpb.Entry) {},
+		SyncTicker: syncTicker.C,
+	}
+	srv.Start()
+	// give time for sync request to be proposed and performed
+	// TODO: use fake clock
+	time.Sleep(syncInterval + time.Millisecond)
+	srv.Stop()
+
+	action := st.Action()
+	if len(action) != 1 {
+		t.Fatalf("len(action) = %d, want 1", len(action))
+	}
+	if action[0] != "DeleteExpiredKeys" {
+		t.Errorf("action = %s, want DeleteExpiredKeys", action[0])
+	}
+}
+
 // TODO: test wait trigger correctness in multi-server case
 
 func TestGetBool(t *testing.T) {
@@ -342,48 +459,63 @@ func TestGetBool(t *testing.T) {
 }
 
 type storeRecorder struct {
+	sync.Mutex
 	action []string
 }
 
+func (s *storeRecorder) record(action string) {
+	s.Lock()
+	s.action = append(s.action, action)
+	s.Unlock()
+}
+func (s *storeRecorder) Action() []string {
+	s.Lock()
+	cpy := make([]string, len(s.action))
+	copy(cpy, s.action)
+	s.Unlock()
+	return cpy
+}
 func (s *storeRecorder) Version() int  { return 0 }
 func (s *storeRecorder) Index() uint64 { return 0 }
 func (s *storeRecorder) Get(_ string, _, _ bool) (*store.Event, error) {
-	s.action = append(s.action, "Get")
+	s.record("Get")
 	return &store.Event{}, nil
 }
 func (s *storeRecorder) Set(_ string, _ bool, _ string, _ time.Time) (*store.Event, error) {
-	s.action = append(s.action, "Set")
+	s.record("Set")
 	return &store.Event{}, nil
 }
 func (s *storeRecorder) Update(_, _ string, _ time.Time) (*store.Event, error) {
-	s.action = append(s.action, "Update")
+	s.record("Update")
 	return &store.Event{}, nil
 }
 func (s *storeRecorder) Create(_ string, _ bool, _ string, _ bool, _ time.Time) (*store.Event, error) {
-	s.action = append(s.action, "Create")
+	s.record("Create")
 	return &store.Event{}, nil
 }
 func (s *storeRecorder) CompareAndSwap(_, _ string, _ uint64, _ string, _ time.Time) (*store.Event, error) {
-	s.action = append(s.action, "CompareAndSwap")
+	s.record("CompareAndSwap")
 	return &store.Event{}, nil
 }
 func (s *storeRecorder) Delete(_ string, _, _ bool) (*store.Event, error) {
-	s.action = append(s.action, "Delete")
+	s.record("Delete")
 	return &store.Event{}, nil
 }
 func (s *storeRecorder) CompareAndDelete(_, _ string, _ uint64) (*store.Event, error) {
-	s.action = append(s.action, "CompareAndDelete")
+	s.record("CompareAndDelete")
 	return &store.Event{}, nil
 }
 func (s *storeRecorder) Watch(_ string, _, _ bool, _ uint64) (store.Watcher, error) {
-	s.action = append(s.action, "Watch")
+	s.record("Watch")
 	return &stubWatcher{}, nil
 }
-func (s *storeRecorder) Save() ([]byte, error)              { return nil, nil }
-func (s *storeRecorder) Recovery(b []byte) error            { return nil }
-func (s *storeRecorder) TotalTransactions() uint64          { return 0 }
-func (s *storeRecorder) JsonStats() []byte                  { return nil }
-func (s *storeRecorder) DeleteExpiredKeys(cutoff time.Time) {}
+func (s *storeRecorder) Save() ([]byte, error)     { return nil, nil }
+func (s *storeRecorder) Recovery(b []byte) error   { return nil }
+func (s *storeRecorder) TotalTransactions() uint64 { return 0 }
+func (s *storeRecorder) JsonStats() []byte         { return nil }
+func (s *storeRecorder) DeleteExpiredKeys(cutoff time.Time) {
+	s.record("DeleteExpiredKeys")
+}
 
 type stubWatcher struct{}
 
diff --git a/functional/http_functional_test.go b/functional/http_functional_test.go
index f3c6751e2..ca5ad9f3d 100644
--- a/functional/http_functional_test.go
+++ b/functional/http_functional_test.go
@@ -17,8 +17,8 @@ import (
 	"github.com/coreos/etcd/third_party/code.google.com/p/go.net/context"
 )
 
-func nopSave(st raftpb.State, ents []raftpb.Entry) {}
-func nopSend(m []raftpb.Message)                   {}
+func nopSave(st raftpb.HardState, ents []raftpb.Entry) {}
+func nopSend(m []raftpb.Message)                       {}
 
 func TestSet(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
@@ -30,7 +30,7 @@ func TestSet(t *testing.T) {
 	srv := &etcdserver.EtcdServer{
 		Store: store.New(),
 		Node:  n,
-		Save:  func(st raftpb.State, ents []raftpb.Entry) {},
+		Save:  func(st raftpb.HardState, ents []raftpb.Entry) {},
 		Send:  etcdserver.SendFunc(nopSend),
 	}
 	srv.Start()
diff --git a/main.go b/main.go
index cb4323be4..1f0323bf4 100644
--- a/main.go
+++ b/main.go
@@ -76,11 +76,12 @@ func startEtcd() http.Handler {
 	n, w := startRaft(id, peers.IDs(), path.Join(*dir, "wal"))
 
 	s := &etcdserver.EtcdServer{
-		Store:  store.New(),
-		Node:   n,
-		Save:   w.Save,
-		Send:   etcdhttp.Sender(*peers),
-		Ticker: time.Tick(100 * time.Millisecond),
+		Store:      store.New(),
+		Node:       n,
+		Save:       w.Save,
+		Send:       etcdhttp.Sender(*peers),
+		Ticker:     time.Tick(100 * time.Millisecond),
+		SyncTicker: time.Tick(500 * time.Millisecond),
 	}
 	s.Start()
 	return etcdhttp.NewHandler(s, *peers, *timeout)
diff --git a/raft/example_test.go b/raft/example_test.go
index efe775d8c..c0726a9f3 100644
--- a/raft/example_test.go
+++ b/raft/example_test.go
@@ -4,10 +4,10 @@ import (
 	pb "github.com/coreos/etcd/raft/raftpb"
 )
 
-func applyToStore(ents []pb.Entry)   {}
-func sendMessages(msgs []pb.Message) {}
-func saveStateToDisk(st pb.State)    {}
-func saveToDisk(ents []pb.Entry)     {}
+func applyToStore(ents []pb.Entry)    {}
+func sendMessages(msgs []pb.Message)  {}
+func saveStateToDisk(st pb.HardState) {}
+func saveToDisk(ents []pb.Entry)      {}
 
 func Example_Node() {
 	n := Start(0, nil, 0, 0)
@@ -15,13 +15,13 @@ func Example_Node() {
 	// stuff to n happens in other goroutines
 
 	// the last known state
-	var prev pb.State
+	var prev pb.HardState
 	for {
 		// ReadState blocks until there is new state ready.
 		rd := <-n.Ready()
-		if !isStateEqual(prev, rd.State) {
-			saveStateToDisk(rd.State)
-			prev = rd.State
+		if !isStateEqual(prev, rd.HardState) {
+			saveStateToDisk(rd.HardState)
+			prev = rd.HardState
 		}
 
 		saveToDisk(rd.Entries)
diff --git a/raft/node.go b/raft/node.go
index a29839c38..b45a8a4cd 100644
--- a/raft/node.go
+++ b/raft/node.go
@@ -9,15 +9,34 @@ import (
 )
 
 var (
-	emptyState = pb.State{}
+	emptyState = pb.HardState{}
 	ErrStopped = errors.New("raft: stopped")
 )
 
-// Ready encapsulates the entries and messages that are ready to be saved to
-// stable storage, committed or sent to other peers.
+// SoftState provides state that is useful for logging and debugging.
+// The state is volatile and does not need to be persisted to the WAL.
+type SoftState struct {
+	Lead      int64
+	RaftState StateType
+}
+
+func (a *SoftState) equal(b *SoftState) bool {
+	return a.Lead == b.Lead && a.RaftState == b.RaftState
+}
+
+// Ready encapsulates the entries and messages that are ready to read,
+// be saved to stable storage, committed or sent to other peers.
+// All fields in Ready are read-only.
 type Ready struct {
-	// The current state of a Node
-	pb.State
+	// The current volatile state of a Node.
+	// SoftState will be nil if there is no update.
+	// It is not required to consume or store SoftState.
+	*SoftState
+
+	// The current state of a Node to be saved to stable storage BEFORE
+	// Messages are sent.
+	// HardState will be equal to empty state if there is no update.
+	pb.HardState
 
 	// Entries specifies entries to be saved to stable storage BEFORE
 	// Messages are sent.
@@ -33,16 +52,16 @@ type Ready struct {
 	Messages []pb.Message
 }
 
-func isStateEqual(a, b pb.State) bool {
+func isStateEqual(a, b pb.HardState) bool {
 	return a.Term == b.Term && a.Vote == b.Vote && a.Commit == b.Commit
 }
 
-func IsEmptyState(st pb.State) bool {
+func IsEmptyState(st pb.HardState) bool {
 	return isStateEqual(st, emptyState)
 }
 
 func (rd Ready) containsUpdates() bool {
-	return !IsEmptyState(rd.State) || len(rd.Entries) > 0 || len(rd.CommittedEntries) > 0 || len(rd.Messages) > 0
+	return rd.SoftState != nil || !IsEmptyState(rd.HardState) || len(rd.Entries) > 0 || len(rd.CommittedEntries) > 0 || len(rd.Messages) > 0
 }
 
 type Node struct {
@@ -65,7 +84,7 @@ func Start(id int64, peers []int64, election, heartbeat int) Node {
 // Restart is identical to Start but takes an initial State and a slice of
 // entries. Generally this is used when restarting from a stable storage
 // log.
-func Restart(id int64, peers []int64, election, heartbeat int, st pb.State, ents []pb.Entry) Node {
+func Restart(id int64, peers []int64, election, heartbeat int, st pb.HardState, ents []pb.Entry) Node {
 	n := newNode()
 	r := newRaft(id, peers, election, heartbeat)
 	r.loadState(st)
@@ -92,13 +111,21 @@ func (n *Node) run(r *raft) {
 	var propc chan pb.Message
 	var readyc chan Ready
 
-	var lead int64
-	prevSt := r.State
+	lead := None
+	prevSoftSt := r.softState()
+	prevHardSt := r.HardState
 
 	for {
-		if lead != r.lead {
-			log.Printf("raft: leader changed from %#x to %#x", lead, r.lead)
-			lead = r.lead
+		rd := newReady(r, prevSoftSt, prevHardSt)
+		if rd.containsUpdates() {
+			readyc = n.readyc
+		} else {
+			readyc = nil
+		}
+
+		if rd.SoftState != nil && lead != rd.SoftState.Lead {
+			log.Printf("raft: leader changed from %#x to %#x", lead, rd.SoftState.Lead)
+			lead = rd.SoftState.Lead
 			if r.hasLeader() {
 				propc = n.propc
 			} else {
@@ -106,13 +133,6 @@ func (n *Node) run(r *raft) {
 			}
 		}
 
-		rd := newReady(r, prevSt)
-		if rd.containsUpdates() {
-			readyc = n.readyc
-		} else {
-			readyc = nil
-		}
-
 		select {
 		case m := <-propc:
 			m.From = r.id
@@ -122,11 +142,14 @@ func (n *Node) run(r *raft) {
 		case <-n.tickc:
 			r.tick()
 		case readyc <- rd:
+			if rd.SoftState != nil {
+				prevSoftSt = rd.SoftState
+			}
+			if !IsEmptyState(rd.HardState) {
+				prevHardSt = rd.HardState
+			}
 			r.raftLog.resetNextEnts()
 			r.raftLog.resetUnstable()
-			if !IsEmptyState(rd.State) {
-				prevSt = rd.State
-			}
 			r.msgs = nil
 		case <-n.done:
 			return
@@ -175,14 +198,17 @@ func (n *Node) Ready() <-chan Ready {
 	return n.readyc
 }
 
-func newReady(r *raft, prev pb.State) Ready {
+func newReady(r *raft, prevSoftSt *SoftState, prevHardSt pb.HardState) Ready {
 	rd := Ready{
 		Entries:          r.raftLog.unstableEnts(),
 		CommittedEntries: r.raftLog.nextEnts(),
 		Messages:         r.msgs,
 	}
-	if !isStateEqual(r.State, prev) {
-		rd.State = r.State
+	if softSt := r.softState(); !softSt.equal(prevSoftSt) {
+		rd.SoftState = softSt
+	}
+	if !isStateEqual(r.HardState, prevHardSt) {
+		rd.HardState = r.HardState
 	}
 	return rd
 }
diff --git a/raft/node_test.go b/raft/node_test.go
index 72fb7816c..65483687e 100644
--- a/raft/node_test.go
+++ b/raft/node_test.go
@@ -121,15 +121,16 @@ func TestReadyContainUpdates(t *testing.T) {
 		wcontain bool
 	}{
 		{Ready{}, false},
-		{Ready{State: raftpb.State{Vote: 1}}, true},
+		{Ready{SoftState: &SoftState{Lead: 1}}, true},
+		{Ready{HardState: raftpb.HardState{Vote: 1}}, true},
 		{Ready{Entries: make([]raftpb.Entry, 1, 1)}, true},
 		{Ready{CommittedEntries: make([]raftpb.Entry, 1, 1)}, true},
 		{Ready{Messages: make([]raftpb.Message, 1, 1)}, true},
 	}
 
 	for i, tt := range tests {
-		if tt.rd.containsUpdates() != tt.wcontain {
-			t.Errorf("#%d: containUpdates = %v, want %v", i, tt.rd.containsUpdates(), tt.wcontain)
+		if g := tt.rd.containsUpdates(); g != tt.wcontain {
+			t.Errorf("#%d: containUpdates = %v, want %v", i, g, tt.wcontain)
 		}
 	}
 }
@@ -140,12 +141,13 @@ func TestNode(t *testing.T) {
 
 	wants := []Ready{
 		{
-			State:            raftpb.State{Term: 1, Commit: 1},
+			SoftState:        &SoftState{Lead: 1, RaftState: StateLeader},
+			HardState:        raftpb.HardState{Term: 1, Commit: 1},
 			Entries:          []raftpb.Entry{{}, {Term: 1, Index: 1}},
 			CommittedEntries: []raftpb.Entry{{Term: 1, Index: 1}},
 		},
 		{
-			State:            raftpb.State{Term: 1, Commit: 2},
+			HardState:        raftpb.HardState{Term: 1, Commit: 2},
 			Entries:          []raftpb.Entry{{Term: 1, Index: 2, Data: []byte("foo")}},
 			CommittedEntries: []raftpb.Entry{{Term: 1, Index: 2, Data: []byte("foo")}},
 		},
@@ -175,10 +177,10 @@ func TestNodeRestart(t *testing.T) {
 		{Term: 1, Index: 1},
 		{Term: 1, Index: 2, Data: []byte("foo")},
 	}
-	st := raftpb.State{Term: 1, Commit: 1}
+	st := raftpb.HardState{Term: 1, Commit: 1}
 
 	want := Ready{
-		State: emptyState,
+		HardState: emptyState,
 		// commit upto index commit index in st
 		CommittedEntries: entries[1 : st.Commit+1],
 	}
@@ -197,13 +199,13 @@ func TestNodeRestart(t *testing.T) {
 
 func TestIsStateEqual(t *testing.T) {
 	tests := []struct {
-		st raftpb.State
+		st raftpb.HardState
 		we bool
 	}{
 		{emptyState, true},
-		{raftpb.State{Vote: 1}, false},
-		{raftpb.State{Commit: 1}, false},
-		{raftpb.State{Term: 1}, false},
+		{raftpb.HardState{Vote: 1}, false},
+		{raftpb.HardState{Commit: 1}, false},
+		{raftpb.HardState{Term: 1}, false},
 	}
 
 	for i, tt := range tests {
diff --git a/raft/raft.go b/raft/raft.go
index 61d1bdd3c..249198094 100644
--- a/raft/raft.go
+++ b/raft/raft.go
@@ -8,7 +8,7 @@ import (
 	pb "github.com/coreos/etcd/raft/raftpb"
 )
 
-const None = 0
+const None int64 = 0
 
 type messageType int64
 
@@ -43,20 +43,20 @@ func (mt messageType) String() string {
 var errNoLeader = errors.New("no leader")
 
 const (
-	stateFollower stateType = iota
-	stateCandidate
-	stateLeader
+	StateFollower StateType = iota
+	StateCandidate
+	StateLeader
 )
 
-type stateType int64
+type StateType int64
 
 var stmap = [...]string{
-	stateFollower:  "stateFollower",
-	stateCandidate: "stateCandidate",
-	stateLeader:    "stateLeader",
+	StateFollower:  "StateFollower",
+	StateCandidate: "StateCandidate",
+	StateLeader:    "StateLeader",
 }
 
-func (st stateType) String() string {
+func (st StateType) String() string {
 	return stmap[int64(st)]
 }
 
@@ -87,7 +87,7 @@ func (p int64Slice) Less(i, j int) bool { return p[i] < p[j] }
 func (p int64Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
 
 type raft struct {
-	pb.State
+	pb.HardState
 
 	id int64
 
@@ -96,7 +96,7 @@ type raft struct {
 
 	prs map[int64]*progress
 
-	state stateType
+	state StateType
 
 	votes map[int64]bool
 
@@ -133,14 +133,18 @@ func newRaft(id int64, peers []int64, election, heartbeat int) *raft {
 
 func (r *raft) hasLeader() bool { return r.lead != None }
 
+func (r *raft) softState() *SoftState {
+	return &SoftState{Lead: r.lead, RaftState: r.state}
+}
+
 func (r *raft) String() string {
 	s := fmt.Sprintf(`state=%v term=%d`, r.state, r.Term)
 	switch r.state {
-	case stateFollower:
+	case StateFollower:
 		s += fmt.Sprintf(" vote=%v lead=%v", r.Vote, r.lead)
-	case stateCandidate:
+	case StateCandidate:
 		s += fmt.Sprintf(` votes="%v"`, r.votes)
-	case stateLeader:
+	case StateLeader:
 		s += fmt.Sprintf(` prs="%v"`, r.prs)
 	}
 	return s
@@ -279,31 +283,31 @@ func (r *raft) becomeFollower(term int64, lead int64) {
 	r.reset(term)
 	r.tick = r.tickElection
 	r.lead = lead
-	r.state = stateFollower
+	r.state = StateFollower
 }
 
 func (r *raft) becomeCandidate() {
 	// TODO(xiangli) remove the panic when the raft implementation is stable
-	if r.state == stateLeader {
+	if r.state == StateLeader {
 		panic("invalid transition [leader -> candidate]")
 	}
 	r.step = stepCandidate
 	r.reset(r.Term + 1)
 	r.tick = r.tickElection
 	r.Vote = r.id
-	r.state = stateCandidate
+	r.state = StateCandidate
 }
 
 func (r *raft) becomeLeader() {
 	// TODO(xiangli) remove the panic when the raft implementation is stable
-	if r.state == stateFollower {
+	if r.state == StateFollower {
 		panic("invalid transition [follower -> leader]")
 	}
 	r.step = stepLeader
 	r.reset(r.Term)
 	r.tick = r.tickHeartbeat
 	r.lead = r.id
-	r.state = stateLeader
+	r.state = StateLeader
 	r.appendEntry(pb.Entry{Data: nil})
 }
 
@@ -504,7 +508,7 @@ func (r *raft) loadEnts(ents []pb.Entry) {
 	r.raftLog.load(ents)
 }
 
-func (r *raft) loadState(state pb.State) {
+func (r *raft) loadState(state pb.HardState) {
 	r.raftLog.committed = state.Commit
 	r.Term = state.Term
 	r.Vote = state.Vote
diff --git a/raft/raft_test.go b/raft/raft_test.go
index 45c062f2a..24c15e622 100644
--- a/raft/raft_test.go
+++ b/raft/raft_test.go
@@ -26,19 +26,19 @@ type Interface interface {
 func TestLeaderElection(t *testing.T) {
 	tests := []struct {
 		*network
-		state stateType
+		state StateType
 	}{
-		{newNetwork(nil, nil, nil), stateLeader},
-		{newNetwork(nil, nil, nopStepper), stateLeader},
-		{newNetwork(nil, nopStepper, nopStepper), stateCandidate},
-		{newNetwork(nil, nopStepper, nopStepper, nil), stateCandidate},
-		{newNetwork(nil, nopStepper, nopStepper, nil, nil), stateLeader},
+		{newNetwork(nil, nil, nil), StateLeader},
+		{newNetwork(nil, nil, nopStepper), StateLeader},
+		{newNetwork(nil, nopStepper, nopStepper), StateCandidate},
+		{newNetwork(nil, nopStepper, nopStepper, nil), StateCandidate},
+		{newNetwork(nil, nopStepper, nopStepper, nil, nil), StateLeader},
 
 		// three logs further along than 0
-		{newNetwork(nil, ents(1), ents(2), ents(1, 3), nil), stateFollower},
+		{newNetwork(nil, ents(1), ents(2), ents(1, 3), nil), StateFollower},
 
 		// logs converge
-		{newNetwork(ents(1), nil, ents(2), ents(1), nil), stateLeader},
+		{newNetwork(ents(1), nil, ents(2), ents(1), nil), StateLeader},
 	}
 
 	for i, tt := range tests {
@@ -226,13 +226,13 @@ func TestDuelingCandidates(t *testing.T) {
 	wlog := &raftLog{ents: []pb.Entry{{}, pb.Entry{Data: nil, Term: 1, Index: 1}}, committed: 1}
 	tests := []struct {
 		sm      *raft
-		state   stateType
+		state   StateType
 		term    int64
 		raftLog *raftLog
 	}{
-		{a, stateFollower, 2, wlog},
-		{b, stateFollower, 2, wlog},
-		{c, stateFollower, 2, newLog()},
+		{a, StateFollower, 2, wlog},
+		{b, StateFollower, 2, wlog},
+		{c, StateFollower, 2, newLog()},
 	}
 
 	for i, tt := range tests {
@@ -269,8 +269,8 @@ func TestCandidateConcede(t *testing.T) {
 	tt.send(pb.Message{From: 3, To: 3, Type: msgProp, Entries: []pb.Entry{{Data: data}}})
 
 	a := tt.peers[1].(*raft)
-	if g := a.state; g != stateFollower {
-		t.Errorf("state = %s, want %s", g, stateFollower)
+	if g := a.state; g != StateFollower {
+		t.Errorf("state = %s, want %s", g, StateFollower)
 	}
 	if g := a.Term; g != 1 {
 		t.Errorf("term = %d, want %d", g, 1)
@@ -293,8 +293,8 @@ func TestSingleNodeCandidate(t *testing.T) {
 	tt.send(pb.Message{From: 1, To: 1, Type: msgHup})
 
 	sm := tt.peers[1].(*raft)
-	if sm.state != stateLeader {
-		t.Errorf("state = %d, want %d", sm.state, stateLeader)
+	if sm.state != StateLeader {
+		t.Errorf("state = %d, want %d", sm.state, StateLeader)
 	}
 }
 
@@ -450,7 +450,7 @@ func TestCommit(t *testing.T) {
 		for j := 0; j < len(tt.matches); j++ {
 			prs[int64(j)] = &progress{tt.matches[j], tt.matches[j] + 1}
 		}
-		sm := &raft{raftLog: &raftLog{ents: tt.logs}, prs: prs, State: pb.State{Term: tt.smTerm}}
+		sm := &raft{raftLog: &raftLog{ents: tt.logs}, prs: prs, HardState: pb.HardState{Term: tt.smTerm}}
 		sm.maybeCommit()
 		if g := sm.raftLog.committed; g != tt.w {
 			t.Errorf("#%d: committed = %d, want %d", i, g, tt.w)
@@ -504,9 +504,9 @@ func TestHandleMsgApp(t *testing.T) {
 
 	for i, tt := range tests {
 		sm := &raft{
-			state:   stateFollower,
-			State:   pb.State{Term: 2},
-			raftLog: &raftLog{committed: 0, ents: []pb.Entry{{}, {Term: 1}, {Term: 2}}},
+			state:     StateFollower,
+			HardState: pb.HardState{Term: 2},
+			raftLog:   &raftLog{committed: 0, ents: []pb.Entry{{}, {Term: 1}, {Term: 2}}},
 		}
 
 		sm.handleAppendEntries(tt.m)
@@ -532,50 +532,50 @@ func TestHandleMsgApp(t *testing.T) {
 
 func TestRecvMsgVote(t *testing.T) {
 	tests := []struct {
-		state   stateType
+		state   StateType
 		i, term int64
 		voteFor int64
 		w       int64
 	}{
-		{stateFollower, 0, 0, None, -1},
-		{stateFollower, 0, 1, None, -1},
-		{stateFollower, 0, 2, None, -1},
-		{stateFollower, 0, 3, None, 2},
+		{StateFollower, 0, 0, None, -1},
+		{StateFollower, 0, 1, None, -1},
+		{StateFollower, 0, 2, None, -1},
+		{StateFollower, 0, 3, None, 2},
 
-		{stateFollower, 1, 0, None, -1},
-		{stateFollower, 1, 1, None, -1},
-		{stateFollower, 1, 2, None, -1},
-		{stateFollower, 1, 3, None, 2},
+		{StateFollower, 1, 0, None, -1},
+		{StateFollower, 1, 1, None, -1},
+		{StateFollower, 1, 2, None, -1},
+		{StateFollower, 1, 3, None, 2},
 
-		{stateFollower, 2, 0, None, -1},
-		{stateFollower, 2, 1, None, -1},
-		{stateFollower, 2, 2, None, 2},
-		{stateFollower, 2, 3, None, 2},
+		{StateFollower, 2, 0, None, -1},
+		{StateFollower, 2, 1, None, -1},
+		{StateFollower, 2, 2, None, 2},
+		{StateFollower, 2, 3, None, 2},
 
-		{stateFollower, 3, 0, None, -1},
-		{stateFollower, 3, 1, None, -1},
-		{stateFollower, 3, 2, None, 2},
-		{stateFollower, 3, 3, None, 2},
+		{StateFollower, 3, 0, None, -1},
+		{StateFollower, 3, 1, None, -1},
+		{StateFollower, 3, 2, None, 2},
+		{StateFollower, 3, 3, None, 2},
 
-		{stateFollower, 3, 2, 2, 2},
-		{stateFollower, 3, 2, 1, -1},
+		{StateFollower, 3, 2, 2, 2},
+		{StateFollower, 3, 2, 1, -1},
 
-		{stateLeader, 3, 3, 1, -1},
-		{stateCandidate, 3, 3, 1, -1},
+		{StateLeader, 3, 3, 1, -1},
+		{StateCandidate, 3, 3, 1, -1},
 	}
 
 	for i, tt := range tests {
 		sm := newRaft(1, []int64{1}, 0, 0)
 		sm.state = tt.state
 		switch tt.state {
-		case stateFollower:
+		case StateFollower:
 			sm.step = stepFollower
-		case stateCandidate:
+		case StateCandidate:
 			sm.step = stepCandidate
-		case stateLeader:
+		case StateLeader:
 			sm.step = stepLeader
 		}
-		sm.State = pb.State{Vote: tt.voteFor}
+		sm.HardState = pb.HardState{Vote: tt.voteFor}
 		sm.raftLog = &raftLog{ents: []pb.Entry{{}, {Term: 2}, {Term: 2}}}
 
 		sm.Step(pb.Message{Type: msgVote, From: 2, Index: tt.i, LogTerm: tt.term})
@@ -593,23 +593,23 @@ func TestRecvMsgVote(t *testing.T) {
 
 func TestStateTransition(t *testing.T) {
 	tests := []struct {
-		from   stateType
-		to     stateType
+		from   StateType
+		to     StateType
 		wallow bool
 		wterm  int64
 		wlead  int64
 	}{
-		{stateFollower, stateFollower, true, 1, None},
-		{stateFollower, stateCandidate, true, 1, None},
-		{stateFollower, stateLeader, false, -1, None},
+		{StateFollower, StateFollower, true, 1, None},
+		{StateFollower, StateCandidate, true, 1, None},
+		{StateFollower, StateLeader, false, -1, None},
 
-		{stateCandidate, stateFollower, true, 0, None},
-		{stateCandidate, stateCandidate, true, 1, None},
-		{stateCandidate, stateLeader, true, 0, 1},
+		{StateCandidate, StateFollower, true, 0, None},
+		{StateCandidate, StateCandidate, true, 1, None},
+		{StateCandidate, StateLeader, true, 0, 1},
 
-		{stateLeader, stateFollower, true, 1, None},
-		{stateLeader, stateCandidate, false, 1, None},
-		{stateLeader, stateLeader, true, 0, 1},
+		{StateLeader, StateFollower, true, 1, None},
+		{StateLeader, StateCandidate, false, 1, None},
+		{StateLeader, StateLeader, true, 0, 1},
 	}
 
 	for i, tt := range tests {
@@ -626,11 +626,11 @@ func TestStateTransition(t *testing.T) {
 			sm.state = tt.from
 
 			switch tt.to {
-			case stateFollower:
+			case StateFollower:
 				sm.becomeFollower(tt.wterm, tt.wlead)
-			case stateCandidate:
+			case StateCandidate:
 				sm.becomeCandidate()
-			case stateLeader:
+			case StateLeader:
 				sm.becomeLeader()
 			}
 
@@ -646,15 +646,15 @@ func TestStateTransition(t *testing.T) {
 
 func TestAllServerStepdown(t *testing.T) {
 	tests := []struct {
-		state stateType
+		state StateType
 
-		wstate stateType
+		wstate StateType
 		wterm  int64
 		windex int64
 	}{
-		{stateFollower, stateFollower, 3, 1},
-		{stateCandidate, stateFollower, 3, 1},
-		{stateLeader, stateFollower, 3, 2},
+		{StateFollower, StateFollower, 3, 1},
+		{StateCandidate, StateFollower, 3, 1},
+		{StateLeader, StateFollower, 3, 2},
 	}
 
 	tmsgTypes := [...]int64{msgVote, msgApp}
@@ -663,11 +663,11 @@ func TestAllServerStepdown(t *testing.T) {
 	for i, tt := range tests {
 		sm := newRaft(1, []int64{1, 2, 3}, 0, 0)
 		switch tt.state {
-		case stateFollower:
+		case StateFollower:
 			sm.becomeFollower(1, None)
-		case stateCandidate:
+		case StateCandidate:
 			sm.becomeCandidate()
-		case stateLeader:
+		case StateLeader:
 			sm.becomeCandidate()
 			sm.becomeLeader()
 		}
@@ -796,13 +796,13 @@ func TestBcastBeat(t *testing.T) {
 // tests the output of the statemachine when receiving msgBeat
 func TestRecvMsgBeat(t *testing.T) {
 	tests := []struct {
-		state stateType
+		state StateType
 		wMsg  int
 	}{
-		{stateLeader, 2},
+		{StateLeader, 2},
 		// candidate and follower should ignore msgBeat
-		{stateCandidate, 0},
-		{stateFollower, 0},
+		{StateCandidate, 0},
+		{StateFollower, 0},
 	}
 
 	for i, tt := range tests {
@@ -811,11 +811,11 @@ func TestRecvMsgBeat(t *testing.T) {
 		sm.Term = 1
 		sm.state = tt.state
 		switch tt.state {
-		case stateFollower:
+		case StateFollower:
 			sm.step = stepFollower
-		case stateCandidate:
+		case StateCandidate:
 			sm.step = stepCandidate
-		case stateLeader:
+		case StateLeader:
 			sm.step = stepLeader
 		}
 		sm.Step(pb.Message{From: 1, To: 1, Type: msgBeat})
diff --git a/raft/raftpb/raft.pb.go b/raft/raftpb/raft.pb.go
index feef8eb25..148c302e2 100644
--- a/raft/raftpb/raft.pb.go
+++ b/raft/raftpb/raft.pb.go
@@ -13,7 +13,7 @@
 		Entry
 		Snapshot
 		Message
-		State
+		HardState
 */
 package raftpb
 
@@ -80,16 +80,16 @@ func (m *Message) Reset()         { *m = Message{} }
 func (m *Message) String() string { return proto.CompactTextString(m) }
 func (*Message) ProtoMessage()    {}
 
-type State struct {
+type HardState struct {
 	Term             int64  `protobuf:"varint,1,req,name=term" json:"term"`
 	Vote             int64  `protobuf:"varint,2,req,name=vote" json:"vote"`
 	Commit           int64  `protobuf:"varint,3,req,name=commit" json:"commit"`
 	XXX_unrecognized []byte `json:"-"`
 }
 
-func (m *State) Reset()         { *m = State{} }
-func (m *State) String() string { return proto.CompactTextString(m) }
-func (*State) ProtoMessage()    {}
+func (m *HardState) Reset()         { *m = HardState{} }
+func (m *HardState) String() string { return proto.CompactTextString(m) }
+func (*HardState) ProtoMessage()    {}
 
 func init() {
 }
@@ -549,7 +549,7 @@ func (m *Message) Unmarshal(data []byte) error {
 	}
 	return nil
 }
-func (m *State) Unmarshal(data []byte) error {
+func (m *HardState) Unmarshal(data []byte) error {
 	l := len(data)
 	index := 0
 	for index < l {
@@ -697,7 +697,7 @@ func (m *Message) Size() (n int) {
 	}
 	return n
 }
-func (m *State) Size() (n int) {
+func (m *HardState) Size() (n int) {
 	var l int
 	_ = l
 	n += 1 + sovRaft(uint64(m.Term))
@@ -879,7 +879,7 @@ func (m *Message) MarshalTo(data []byte) (n int, err error) {
 	}
 	return i, nil
 }
-func (m *State) Marshal() (data []byte, err error) {
+func (m *HardState) Marshal() (data []byte, err error) {
 	size := m.Size()
 	data = make([]byte, size)
 	n, err := m.MarshalTo(data)
@@ -889,7 +889,7 @@ func (m *State) Marshal() (data []byte, err error) {
 	return data[:n], nil
 }
 
-func (m *State) MarshalTo(data []byte) (n int, err error) {
+func (m *HardState) MarshalTo(data []byte) (n int, err error) {
 	var i int
 	_ = i
 	var l int
diff --git a/raft/raftpb/raft.proto b/raft/raftpb/raft.proto
index e254ebab7..d6bf94ab0 100644
--- a/raft/raftpb/raft.proto
+++ b/raft/raftpb/raft.proto
@@ -36,7 +36,7 @@ message Message {
 	required Snapshot snapshot = 9 [(gogoproto.nullable) = false];
 }
 
-message State {
+message HardState {
 	required int64 term   = 1 [(gogoproto.nullable) = false];
 	required int64 vote   = 2 [(gogoproto.nullable) = false];
 	required int64 commit = 3 [(gogoproto.nullable) = false];
diff --git a/wal/decoder.go b/wal/decoder.go
index 4921f5ba6..3d243e9e6 100644
--- a/wal/decoder.go
+++ b/wal/decoder.go
@@ -76,8 +76,8 @@ func mustUnmarshalEntry(d []byte) raftpb.Entry {
 	return e
 }
 
-func mustUnmarshalState(d []byte) raftpb.State {
-	var s raftpb.State
+func mustUnmarshalState(d []byte) raftpb.HardState {
+	var s raftpb.HardState
 	if err := s.Unmarshal(d); err != nil {
 		panic(err)
 	}
diff --git a/wal/wal.go b/wal/wal.go
index d369a23c9..47c22d2eb 100644
--- a/wal/wal.go
+++ b/wal/wal.go
@@ -153,7 +153,7 @@ func OpenAtIndex(dirpath string, index int64) (*WAL, error) {
 
 // ReadAll reads out all records of the current WAL.
 // After ReadAll, the WAL will be ready for appending new records.
-func (w *WAL) ReadAll() (id int64, state raftpb.State, ents []raftpb.Entry, err error) {
+func (w *WAL) ReadAll() (id int64, state raftpb.HardState, ents []raftpb.Entry, err error) {
 	rec := &walpb.Record{}
 	decoder := w.decoder
 
@@ -264,7 +264,7 @@ func (w *WAL) SaveEntry(e *raftpb.Entry) error {
 	return nil
 }
 
-func (w *WAL) SaveState(s *raftpb.State) error {
+func (w *WAL) SaveState(s *raftpb.HardState) error {
 	if raft.IsEmptyState(*s) {
 		return nil
 	}
@@ -277,7 +277,7 @@ func (w *WAL) SaveState(s *raftpb.State) error {
 	return w.encoder.encode(rec)
 }
 
-func (w *WAL) Save(st raftpb.State, ents []raftpb.Entry) {
+func (w *WAL) Save(st raftpb.HardState, ents []raftpb.Entry) {
 	// TODO(xiangli): no more reference operator
 	w.SaveState(&st)
 	for i := range ents {
diff --git a/wal/wal_test.go b/wal/wal_test.go
index 49580cf14..9fbefbec6 100644
--- a/wal/wal_test.go
+++ b/wal/wal_test.go
@@ -175,7 +175,7 @@ func TestRecover(t *testing.T) {
 			t.Fatal(err)
 		}
 	}
-	sts := []raftpb.State{{Term: 1, Vote: 1, Commit: 1}, {Term: 2, Vote: 2, Commit: 2}}
+	sts := []raftpb.HardState{{Term: 1, Vote: 1, Commit: 1}, {Term: 2, Vote: 2, Commit: 2}}
 	for _, s := range sts {
 		if err = w.SaveState(&s); err != nil {
 			t.Fatal(err)
@@ -341,7 +341,7 @@ func TestRecoverAfterCut(t *testing.T) {
 
 func TestSaveEmpty(t *testing.T) {
 	var buf bytes.Buffer
-	var est raftpb.State
+	var est raftpb.HardState
 	w := WAL{
 		encoder: newEncoder(&buf, 0),
 	}