diff --git a/weed/topology/node.go b/weed/topology/node.go
index a23729dd3..4556b4165 100644
--- a/weed/topology/node.go
+++ b/weed/topology/node.go
@@ -242,9 +242,9 @@ func (n *NodeImpl) CollectDeadNodeAndFullVolumes(freshThreshHold int64, volumeSi
 			for _, v := range dn.GetVolumes() {
 				if v.Size >= volumeSizeLimit {
 					//fmt.Println("volume",v.Id,"size",v.Size,">",volumeSizeLimit)
-					n.GetTopology().chanFullVolumes <- &v
+					n.GetTopology().chanFullVolumes <- v
 				}else if float64(v.Size) > float64(volumeSizeLimit) * growThreshold {
-					n.GetTopology().chanCrowdedVolumes <- &v
+					n.GetTopology().chanCrowdedVolumes <- v
 				}
 			}
 		}
diff --git a/weed/topology/topology.go b/weed/topology/topology.go
index 3932e3fbb..d704a5636 100644
--- a/weed/topology/topology.go
+++ b/weed/topology/topology.go
@@ -34,8 +34,8 @@ type Topology struct {
 
 	Sequence sequence.Sequencer
 
-	chanFullVolumes    chan *storage.VolumeInfo
-	chanCrowdedVolumes chan *storage.VolumeInfo
+	chanFullVolumes    chan storage.VolumeInfo
+	chanCrowdedVolumes chan storage.VolumeInfo
 
 	Configuration      *Configuration
 
@@ -57,8 +57,8 @@ func NewTopology(id string, seq sequence.Sequencer, volumeSizeLimit uint64, puls
 
 	t.Sequence = seq
 
-	t.chanFullVolumes = make(chan *storage.VolumeInfo)
-	t.chanCrowdedVolumes = make(chan *storage.VolumeInfo)
+	t.chanFullVolumes = make(chan storage.VolumeInfo)
+	t.chanCrowdedVolumes = make(chan storage.VolumeInfo)
 
 	t.Configuration = &Configuration{}
 
diff --git a/weed/topology/topology_event_handling.go b/weed/topology/topology_event_handling.go
index 2f4fba932..0f1db74df 100644
--- a/weed/topology/topology_event_handling.go
+++ b/weed/topology/topology_event_handling.go
@@ -39,7 +39,7 @@ func (t *Topology) StartRefreshWritableVolumes(grpcDialOption grpc.DialOption, g
 		}
 	}()
 }
-func (t *Topology) SetVolumeCapacityFull(volumeInfo *storage.VolumeInfo) bool {
+func (t *Topology) SetVolumeCapacityFull(volumeInfo storage.VolumeInfo) bool {
 	diskType := types.ToDiskType(volumeInfo.DiskType)
 	vl := t.GetVolumeLayout(volumeInfo.Collection, volumeInfo.ReplicaPlacement, volumeInfo.Ttl, diskType)
 	if !vl.SetVolumeCapacityFull(volumeInfo.Id) {
@@ -68,7 +68,7 @@ func (t *Topology) SetVolumeCapacityFull(volumeInfo *storage.VolumeInfo) bool {
 	return true
 }
 
-func (t *Topology) SetVolumeCrowded(volumeInfo *storage.VolumeInfo) {
+func (t *Topology) SetVolumeCrowded(volumeInfo storage.VolumeInfo) {
 	diskType := types.ToDiskType(volumeInfo.DiskType)
 	vl := t.GetVolumeLayout(volumeInfo.Collection, volumeInfo.ReplicaPlacement, volumeInfo.Ttl, diskType)
 	vl.SetVolumeCrowded(volumeInfo.Id)
diff --git a/weed/topology/volume_layout.go b/weed/topology/volume_layout.go
index 57e511fa0..f315cb7e4 100644
--- a/weed/topology/volume_layout.go
+++ b/weed/topology/volume_layout.go
@@ -108,7 +108,7 @@ type VolumeLayout struct {
 	diskType         types.DiskType
 	vid2location     map[needle.VolumeId]*VolumeLocationList
 	writables        []needle.VolumeId // transient array of writable volume id
-	crowded          map[needle.VolumeId]interface{}
+	crowded          map[needle.VolumeId]struct{}
 	readonlyVolumes  *volumesBinaryState // readonly volumes
 	oversizedVolumes *volumesBinaryState // oversized volumes
 	volumeSizeLimit  uint64
@@ -129,7 +129,7 @@ func NewVolumeLayout(rp *super_block.ReplicaPlacement, ttl *needle.TTL, diskType
 		diskType:         diskType,
 		vid2location:     make(map[needle.VolumeId]*VolumeLocationList),
 		writables:        *new([]needle.VolumeId),
-		crowded:          make(map[needle.VolumeId]interface{}),
+		crowded:          make(map[needle.VolumeId]struct{}),
 		readonlyVolumes:  NewVolumesBinaryState(readOnlyState, rp, ExistCopies()),
 		oversizedVolumes: NewVolumesBinaryState(oversizedState, rp, ExistCopies()),
 		volumeSizeLimit:  volumeSizeLimit,
@@ -421,7 +421,7 @@ func (vl *VolumeLayout) removeFromCrowded(vid needle.VolumeId) {
 
 func (vl *VolumeLayout) setVolumeCrowded(vid needle.VolumeId) {
 	if _, ok := vl.crowded[vid]; !ok {
-		vl.crowded[vid] = nil
+		vl.crowded[vid] = struct{}{}
 		glog.V(0).Infoln("Volume", vid, "becomes crowded")
 	}
 }