diff --git a/weed/command/benchmark.go b/weed/command/benchmark.go
index af5919adf..7091463cc 100644
--- a/weed/command/benchmark.go
+++ b/weed/command/benchmark.go
@@ -129,7 +129,7 @@ func runBenchmark(cmd *Command, args []string) bool {
 		defer pprof.StopCPUProfile()
 	}
 
-	b.masterClient = wdclient.NewMasterClient(b.grpcDialOption, "client", "", "", pb.ServerAddresses(*b.masters).ToAddresses())
+	b.masterClient = wdclient.NewMasterClient(b.grpcDialOption, "client", "", "", pb.ServerAddresses(*b.masters).ToAddressMap())
 	go b.masterClient.KeepConnectedToMaster()
 	b.masterClient.WaitUntilConnected()
 
diff --git a/weed/command/filer.go b/weed/command/filer.go
index 4f8fd947a..0a768944b 100644
--- a/weed/command/filer.go
+++ b/weed/command/filer.go
@@ -29,7 +29,7 @@ var (
 )
 
 type FilerOptions struct {
-	masters                 []pb.ServerAddress
+	masters                 map[string]pb.ServerAddress
 	mastersString           *string
 	ip                      *string
 	bindIp                  *string
@@ -171,7 +171,7 @@ func runFiler(cmd *Command, args []string) bool {
 		}()
 	}
 
-	f.masters = pb.ServerAddresses(*f.mastersString).ToAddresses()
+	f.masters = pb.ServerAddresses(*f.mastersString).ToAddressMap()
 
 	f.startFiler()
 
diff --git a/weed/command/iam.go b/weed/command/iam.go
index 88b17b1a2..968d23095 100644
--- a/weed/command/iam.go
+++ b/weed/command/iam.go
@@ -67,7 +67,7 @@ func (iamopt *IamOptions) startIamServer() bool {
 		}
 	}
 
-	masters := pb.ServerAddresses(*iamopt.masters).ToAddresses()
+	masters := pb.ServerAddresses(*iamopt.masters).ToAddressMap()
 	router := mux.NewRouter().SkipClean(true)
 	_, iamApiServer_err := iamapi.NewIamApiServer(router, &iamapi.IamServerOption{
 		Masters:        masters,
diff --git a/weed/command/master.go b/weed/command/master.go
index 9792ce0ba..e56ee19fe 100644
--- a/weed/command/master.go
+++ b/weed/command/master.go
@@ -132,8 +132,13 @@ func startMaster(masterOption MasterOptions, masterWhiteList []string) {
 
 	myMasterAddress, peers := checkPeers(*masterOption.ip, *masterOption.port, *masterOption.portGrpc, *masterOption.peers)
 
+	masterPeers := make(map[string]pb.ServerAddress)
+	for _, peer := range peers {
+		masterPeers[peer.String()] = peer
+	}
+
 	r := mux.NewRouter()
-	ms := weed_server.NewMasterServer(r, masterOption.toMasterOption(masterWhiteList), peers)
+	ms := weed_server.NewMasterServer(r, masterOption.toMasterOption(masterWhiteList), masterPeers)
 	listeningAddress := util.JoinHostPort(*masterOption.ipBind, *masterOption.port)
 	glog.V(0).Infof("Start Seaweed Master %s at %s", util.Version(), listeningAddress)
 	masterListener, masterLocalListner, e := util.NewIpAndLocalListeners(*masterOption.ipBind, *masterOption.port, 0)
@@ -141,11 +146,6 @@ func startMaster(masterOption MasterOptions, masterWhiteList []string) {
 		glog.Fatalf("Master startup error: %v", e)
 	}
 
-	masterPeers := make(map[string]pb.ServerAddress)
-	for _, peer := range peers {
-		masterPeers[peer.String()] = peer
-	}
-
 	// start raftServer
 	raftServerOption := &weed_server.RaftServerOption{
 		GrpcDialOption:    security.LoadClientTLS(util.GetViper(), "grpc.master"),
diff --git a/weed/command/master_follower.go b/weed/command/master_follower.go
index f182d7ce4..ec7d2758f 100644
--- a/weed/command/master_follower.go
+++ b/weed/command/master_follower.go
@@ -83,7 +83,7 @@ func runMasterFollower(cmd *Command, args []string) bool {
 func startMasterFollower(masterOptions MasterOptions) {
 
 	// collect settings from main masters
-	masters := pb.ServerAddresses(*mf.peers).ToAddresses()
+	masters := pb.ServerAddresses(*mf.peers).ToAddressMap()
 
 	var err error
 	grpcDialOption := security.LoadClientTLS(util.GetViper(), "grpc.master")
diff --git a/weed/command/server.go b/weed/command/server.go
index a1b495c5f..0cc60fd30 100644
--- a/weed/command/server.go
+++ b/weed/command/server.go
@@ -191,7 +191,7 @@ func runServer(cmd *Command, args []string) bool {
 	// ip address
 	masterOptions.ip = serverIp
 	masterOptions.ipBind = serverBindIp
-	filerOptions.masters = pb.ServerAddresses(*masterOptions.peers).ToAddresses()
+	filerOptions.masters = pb.ServerAddresses(*masterOptions.peers).ToAddressMap()
 	filerOptions.ip = serverIp
 	filerOptions.bindIp = serverBindIp
 	s3Options.bindIp = serverBindIp
diff --git a/weed/filer/filer.go b/weed/filer/filer.go
index 7b6f1342c..836a0e447 100644
--- a/weed/filer/filer.go
+++ b/weed/filer/filer.go
@@ -49,7 +49,7 @@ type Filer struct {
 	UniqueFileId        uint32
 }
 
-func NewFiler(masters []pb.ServerAddress, grpcDialOption grpc.DialOption,
+func NewFiler(masters map[string]pb.ServerAddress, grpcDialOption grpc.DialOption,
 	filerHost pb.ServerAddress, collection string, replication string, dataCenter string, notifyFn func()) *Filer {
 	f := &Filer{
 		MasterClient:        wdclient.NewMasterClient(grpcDialOption, cluster.FilerType, filerHost, dataCenter, masters),
diff --git a/weed/iamapi/iamapi_server.go b/weed/iamapi/iamapi_server.go
index fc0e6b700..6f6cc7533 100644
--- a/weed/iamapi/iamapi_server.go
+++ b/weed/iamapi/iamapi_server.go
@@ -33,7 +33,7 @@ type IamS3ApiConfigure struct {
 }
 
 type IamServerOption struct {
-	Masters        []pb.ServerAddress
+	Masters        map[string]pb.ServerAddress
 	Filer          pb.ServerAddress
 	Port           int
 	GrpcDialOption grpc.DialOption
diff --git a/weed/pb/grpc_client_server.go b/weed/pb/grpc_client_server.go
index cedcc2813..50feb2e23 100644
--- a/weed/pb/grpc_client_server.go
+++ b/weed/pb/grpc_client_server.go
@@ -206,7 +206,7 @@ func WithMasterClient(streamingMode bool, master ServerAddress, grpcDialOption g
 
 }
 
-func WithOneOfGrpcMasterClients(streamingMode bool, masterGrpcAddresses []ServerAddress, grpcDialOption grpc.DialOption, fn func(client master_pb.SeaweedClient) error) (err error) {
+func WithOneOfGrpcMasterClients(streamingMode bool, masterGrpcAddresses map[string]ServerAddress, grpcDialOption grpc.DialOption, fn func(client master_pb.SeaweedClient) error) (err error) {
 
 	for _, masterGrpcAddress := range masterGrpcAddresses {
 		err = WithGrpcClient(streamingMode, func(grpcConnection *grpc.ClientConn) error {
diff --git a/weed/pb/server_address.go b/weed/pb/server_address.go
index b60551c71..c7faea4bd 100644
--- a/weed/pb/server_address.go
+++ b/weed/pb/server_address.go
@@ -86,6 +86,14 @@ func (sa ServerAddresses) ToAddresses() (addresses []ServerAddress) {
 	return
 }
 
+func (sa ServerAddresses) ToAddressMap() (addresses map[string]ServerAddress) {
+	addresses = make(map[string]ServerAddress)
+	for _, address := range sa.ToAddresses() {
+		addresses[address.String()] = address
+	}
+	return
+}
+
 func (sa ServerAddresses) ToAddressStrings() (addresses []string) {
 	parts := strings.Split(string(sa), ",")
 	for _, address := range parts {
@@ -101,6 +109,13 @@ func ToAddressStrings(addresses []ServerAddress) []string {
 	}
 	return strings
 }
+func ToAddressStringsFromMap(addresses map[string]ServerAddress) []string {
+	var strings []string
+	for _, addr := range addresses {
+		strings = append(strings, string(addr))
+	}
+	return strings
+}
 func FromAddressStrings(strings []string) []ServerAddress {
 	var addresses []ServerAddress
 	for _, addr := range strings {
diff --git a/weed/server/filer_grpc_server.go b/weed/server/filer_grpc_server.go
index 3f65660ee..5a5714156 100644
--- a/weed/server/filer_grpc_server.go
+++ b/weed/server/filer_grpc_server.go
@@ -393,7 +393,7 @@ func (fs *FilerServer) GetFilerConfiguration(ctx context.Context, req *filer_pb.
 	clusterId, _ := fs.filer.Store.KvGet(context.Background(), []byte("clusterId"))
 
 	t := &filer_pb.GetFilerConfigurationResponse{
-		Masters:            pb.ToAddressStrings(fs.option.Masters),
+		Masters:            pb.ToAddressStringsFromMap(fs.option.Masters),
 		Collection:         fs.option.Collection,
 		Replication:        fs.option.DefaultReplication,
 		MaxMb:              uint32(fs.option.MaxMB),
diff --git a/weed/server/filer_server.go b/weed/server/filer_server.go
index 497f59568..7edd5870f 100644
--- a/weed/server/filer_server.go
+++ b/weed/server/filer_server.go
@@ -48,7 +48,7 @@ import (
 )
 
 type FilerOption struct {
-	Masters               []pb.ServerAddress
+	Masters               map[string]pb.ServerAddress
 	Collection            string
 	DefaultReplication    string
 	DisableDirListing     bool
diff --git a/weed/server/master_server.go b/weed/server/master_server.go
index 671432d5c..b63e3a418 100644
--- a/weed/server/master_server.go
+++ b/weed/server/master_server.go
@@ -75,7 +75,7 @@ type MasterServer struct {
 	Cluster *cluster.Cluster
 }
 
-func NewMasterServer(r *mux.Router, option *MasterOption, peers []pb.ServerAddress) *MasterServer {
+func NewMasterServer(r *mux.Router, option *MasterOption, peers map[string]pb.ServerAddress) *MasterServer {
 
 	v := util.GetViper()
 	signingKey := v.GetString("jwt.signing.key")
diff --git a/weed/shell/commands.go b/weed/shell/commands.go
index ec71edee0..3ff49f1d2 100644
--- a/weed/shell/commands.go
+++ b/weed/shell/commands.go
@@ -46,7 +46,7 @@ var (
 func NewCommandEnv(options *ShellOptions) *CommandEnv {
 	ce := &CommandEnv{
 		env:          make(map[string]string),
-		MasterClient: wdclient.NewMasterClient(options.GrpcDialOption, pb.AdminShellClient, "", "", pb.ServerAddresses(*options.Masters).ToAddresses()),
+		MasterClient: wdclient.NewMasterClient(options.GrpcDialOption, pb.AdminShellClient, "", "", pb.ServerAddresses(*options.Masters).ToAddressMap()),
 		option:       options,
 	}
 	ce.locker = exclusive_locks.NewExclusiveLocker(ce.MasterClient, "admin")
diff --git a/weed/wdclient/masterclient.go b/weed/wdclient/masterclient.go
index 5280305e2..daf74c1be 100644
--- a/weed/wdclient/masterclient.go
+++ b/weed/wdclient/masterclient.go
@@ -18,7 +18,7 @@ type MasterClient struct {
 	clientType     string
 	clientHost     pb.ServerAddress
 	currentMaster  pb.ServerAddress
-	masters        []pb.ServerAddress
+	masters        map[string]pb.ServerAddress
 	grpcDialOption grpc.DialOption
 
 	vidMap
@@ -26,7 +26,7 @@ type MasterClient struct {
 	OnPeerUpdate func(update *master_pb.ClusterNodeUpdate)
 }
 
-func NewMasterClient(grpcDialOption grpc.DialOption, clientType string, clientHost pb.ServerAddress, clientDataCenter string, masters []pb.ServerAddress) *MasterClient {
+func NewMasterClient(grpcDialOption grpc.DialOption, clientType string, clientHost pb.ServerAddress, clientDataCenter string, masters map[string]pb.ServerAddress) *MasterClient {
 	return &MasterClient{
 		clientType:     clientType,
 		clientHost:     clientHost,