diff --git a/weed/cluster/cluster.go b/weed/cluster/cluster.go
index fa01bd03d..e8752f4d9 100644
--- a/weed/cluster/cluster.go
+++ b/weed/cluster/cluster.go
@@ -9,9 +9,10 @@ import (
 )
 
 const (
-	MasterType = "master"
-	FilerType  = "filer"
-	BrokerType = "broker"
+	MasterType       = "master"
+	VolumeServerType = "volumeServer"
+	FilerType        = "filer"
+	BrokerType       = "broker"
 )
 
 type ClusterNode struct {
diff --git a/weed/server/filer_grpc_server_admin.go b/weed/server/filer_grpc_server_admin.go
index ee3394a77..2a6f74eee 100644
--- a/weed/server/filer_grpc_server_admin.go
+++ b/weed/server/filer_grpc_server_admin.go
@@ -3,6 +3,7 @@ package weed_server
 import (
 	"context"
 	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/cluster"
 	"github.com/chrislusf/seaweedfs/weed/glog"
 	"github.com/chrislusf/seaweedfs/weed/pb"
 	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
@@ -43,19 +44,19 @@ func (fs *FilerServer) Statistics(ctx context.Context, req *filer_pb.StatisticsR
 
 func (fs *FilerServer) Ping(ctx context.Context, req *filer_pb.PingRequest) (resp *filer_pb.PingResponse, pingErr error) {
 	resp = &filer_pb.PingResponse{}
-	if req.TargetType == "Filer" {
+	if req.TargetType == cluster.FilerType {
 		pingErr = pb.WithFilerClient(false, pb.ServerAddress(req.Target), fs.grpcDialOption, func(client filer_pb.SeaweedFilerClient) error {
 			_, err := client.Ping(ctx, &filer_pb.PingRequest{})
 			return err
 		})
 	}
-	if req.TargetType == "VolumeServer" {
+	if req.TargetType == cluster.VolumeServerType {
 		pingErr = pb.WithVolumeServerClient(false, pb.ServerAddress(req.Target), fs.grpcDialOption, func(client volume_server_pb.VolumeServerClient) error {
 			_, err := client.Ping(ctx, &volume_server_pb.PingRequest{})
 			return err
 		})
 	}
-	if req.TargetType == "Master" {
+	if req.TargetType == cluster.MasterType {
 		pingErr = pb.WithMasterClient(false, pb.ServerAddress(req.Target), fs.grpcDialOption, func(client master_pb.SeaweedClient) error {
 			_, err := client.Ping(ctx, &master_pb.PingRequest{})
 			return err
diff --git a/weed/server/master_grpc_server_admin.go b/weed/server/master_grpc_server_admin.go
index 0649ea73e..153e48129 100644
--- a/weed/server/master_grpc_server_admin.go
+++ b/weed/server/master_grpc_server_admin.go
@@ -3,6 +3,7 @@ package weed_server
 import (
 	"context"
 	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/cluster"
 	"github.com/chrislusf/seaweedfs/weed/glog"
 	"github.com/chrislusf/seaweedfs/weed/pb"
 	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
@@ -148,19 +149,19 @@ func (ms *MasterServer) ReleaseAdminToken(ctx context.Context, req *master_pb.Re
 
 func (ms *MasterServer) Ping(ctx context.Context, req *master_pb.PingRequest) (resp *master_pb.PingResponse, pingErr error) {
 	resp = &master_pb.PingResponse{}
-	if req.TargetType == "Filer" {
+	if req.TargetType == cluster.FilerType {
 		pingErr = pb.WithFilerClient(false, pb.ServerAddress(req.Target), ms.grpcDialOption, func(client filer_pb.SeaweedFilerClient) error {
 			_, err := client.Ping(ctx, &filer_pb.PingRequest{})
 			return err
 		})
 	}
-	if req.TargetType == "VolumeServer" {
+	if req.TargetType == cluster.VolumeServerType {
 		pingErr = pb.WithVolumeServerClient(false, pb.ServerAddress(req.Target), ms.grpcDialOption, func(client volume_server_pb.VolumeServerClient) error {
 			_, err := client.Ping(ctx, &volume_server_pb.PingRequest{})
 			return err
 		})
 	}
-	if req.TargetType == "Master" {
+	if req.TargetType == cluster.MasterType {
 		pingErr = pb.WithMasterClient(false, pb.ServerAddress(req.Target), ms.grpcDialOption, func(client master_pb.SeaweedClient) error {
 			_, err := client.Ping(ctx, &master_pb.PingRequest{})
 			return err
diff --git a/weed/server/volume_grpc_admin.go b/weed/server/volume_grpc_admin.go
index a6617bfe1..09da32f7a 100644
--- a/weed/server/volume_grpc_admin.go
+++ b/weed/server/volume_grpc_admin.go
@@ -3,6 +3,7 @@ package weed_server
 import (
 	"context"
 	"fmt"
+	"github.com/chrislusf/seaweedfs/weed/cluster"
 	"github.com/chrislusf/seaweedfs/weed/pb"
 	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
 	"github.com/chrislusf/seaweedfs/weed/pb/master_pb"
@@ -253,19 +254,19 @@ func (vs *VolumeServer) VolumeNeedleStatus(ctx context.Context, req *volume_serv
 
 func (vs *VolumeServer) Ping(ctx context.Context, req *volume_server_pb.PingRequest) (resp *volume_server_pb.PingResponse, pingErr error) {
 	resp = &volume_server_pb.PingResponse{}
-	if req.TargetType == "Filer" {
+	if req.TargetType == cluster.FilerType {
 		pingErr = pb.WithFilerClient(false, pb.ServerAddress(req.Target), vs.grpcDialOption, func(client filer_pb.SeaweedFilerClient) error {
 			_, err := client.Ping(ctx, &filer_pb.PingRequest{})
 			return err
 		})
 	}
-	if req.TargetType == "VolumeServer" {
+	if req.TargetType == cluster.VolumeServerType {
 		pingErr = pb.WithVolumeServerClient(false, pb.ServerAddress(req.Target), vs.grpcDialOption, func(client volume_server_pb.VolumeServerClient) error {
 			_, err := client.Ping(ctx, &volume_server_pb.PingRequest{})
 			return err
 		})
 	}
-	if req.TargetType == "Master" {
+	if req.TargetType == cluster.MasterType {
 		pingErr = pb.WithMasterClient(false, pb.ServerAddress(req.Target), vs.grpcDialOption, func(client master_pb.SeaweedClient) error {
 			_, err := client.Ping(ctx, &master_pb.PingRequest{})
 			return err