diff --git a/README.MD b/README.MD
index 4a340cb5..1a21cc54 100644
--- a/README.MD
+++ b/README.MD
@@ -84,6 +84,8 @@ port: 4000
 cluster_id: ${CLUSTER_ID}
 # CLUSTER_SECRET
 cluster_secret: ${CLUSTER_SECRET}
+# 文件同步间隔 (分钟)
+sync_interval: 10
 # 同步文件时最多打开的连接数量
 download_max_conn: 64
 # 服务器上行限制
diff --git a/cluster.go b/cluster.go
index d66bf00a..4d1d32c2 100644
--- a/cluster.go
+++ b/cluster.go
@@ -239,18 +239,19 @@ func (cr *Cluster) Enable(ctx context.Context) (err error) {
 	var keepaliveCtx context.Context
 	keepaliveCtx, cr.cancelKeepalive = context.WithCancel(ctx)
 	createInterval(keepaliveCtx, func() {
-		ctx, cancel := context.WithTimeout(keepaliveCtx, KeepAliveInterval/2)
-		defer cancel()
-		if !cr.KeepAlive(ctx) {
+		tctx, cancel := context.WithTimeout(keepaliveCtx, KeepAliveInterval/2)
+		ok := cr.KeepAlive(tctx)
+		cancel()
+		if !ok {
 			if keepaliveCtx.Err() == nil {
 				logInfo("Reconnecting due to keepalive failed")
-				cr.Disable(keepaliveCtx)
+				cr.Disable(ctx)
 				logInfo("Reconnecting ...")
-				if !cr.Connect(keepaliveCtx) {
+				if !cr.Connect(ctx) {
 					logError("Cannot reconnect to server, exit.")
 					os.Exit(1)
 				}
-				if err := cr.Enable(keepaliveCtx); err != nil {
+				if err := cr.Enable(ctx); err != nil {
 					logError("Cannot enable cluster:", err, "; exit.")
 					os.Exit(1)
 				}
diff --git a/cluster_oss.go b/cluster_oss.go
index 99e6bc0c..723feca1 100644
--- a/cluster_oss.go
+++ b/cluster_oss.go
@@ -96,6 +96,11 @@ func (cr *Cluster) ossSyncFiles(ctx context.Context, files []FileInfo) error {
 			case path := <-pathRes:
 				if path != "" {
 					defer os.Remove(path)
+					// acquire slot here
+					buf := <-stats.slots
+					defer func(){
+						stats.slots <- buf
+					}()
 					var srcFd *os.File
 					if srcFd, err = os.Open(path); err != nil {
 						return
@@ -113,7 +118,7 @@ func (cr *Cluster) ossSyncFiles(ctx context.Context, files []FileInfo) error {
 							logErrorf("Could not seek file %q: %v", path, err)
 							continue
 						}
-						_, err = io.Copy(dstFd, srcFd)
+						_, err = io.CopyBuffer(dstFd, srcFd, buf)
 						dstFd.Close()
 						if err != nil {
 							logErrorf("Could not copy from %q to %q:\n\t%v", path, target, err)
diff --git a/config.go b/config.go
index c27e7372..ba15f8f2 100644
--- a/config.go
+++ b/config.go
@@ -66,6 +66,7 @@ type Config struct {
 	Port            uint16           `yaml:"port"`
 	ClusterId       string           `yaml:"cluster_id"`
 	ClusterSecret   string           `yaml:"cluster_secret"`
+	SyncInterval    int              `yaml:"sync_interval"`
 	DownloadMaxConn int              `yaml:"download_max_conn"`
 	ServeLimit      ServeLimitConfig `yaml:"serve_limit"`
 	Oss             OSSConfig        `yaml:"oss"`
@@ -84,6 +85,7 @@ func readConfig() (config Config) {
 		Port:            4000,
 		ClusterId:       "${CLUSTER_ID}",
 		ClusterSecret:   "${CLUSTER_SECRET}",
+		SyncInterval:    10,
 		DownloadMaxConn: 64,
 		ServeLimit: ServeLimitConfig{
 			Enable:     false,
diff --git a/config.yaml b/config.yaml
index ab12a8c2..659f979c 100644
--- a/config.yaml
+++ b/config.yaml
@@ -7,6 +7,7 @@ public_port: 8080
 port: 4000
 cluster_id: ${CLUSTER_ID}
 cluster_secret: ${CLUSTER_SECRET}
+sync_interval: 10
 download_max_conn: 64
 serve_limit:
     enable: false
diff --git a/main.go b/main.go
index ccd48262..43e21b16 100644
--- a/main.go
+++ b/main.go
@@ -34,7 +34,6 @@ import (
 )
 
 var (
-	SyncFileInterval  = time.Minute * 10
 	KeepAliveInterval = time.Second * 59
 )
 
@@ -252,7 +251,7 @@ START:
 				return
 			}
 			cluster.SyncFiles(ctx, fl)
-		}, SyncFileInterval)
+		}, (time.Duration)(config.SyncInterval)*time.Minute)
 
 		if err := cluster.Enable(ctx); err != nil {
 			logError("Cannot enable cluster:", err)