diff --git a/weed/topology/volume_layout.go b/weed/topology/volume_layout.go
index f315cb7e4..db05102fe 100644
--- a/weed/topology/volume_layout.go
+++ b/weed/topology/volume_layout.go
@@ -302,7 +302,7 @@ func (vl *VolumeLayout) PickForWrite(count uint64, option *VolumeGrowOption) (*n
 				}
 				counter++
 				if rand.Intn(counter) < 1 {
-					vid, locationList = v, volumeLocationList
+					vid, locationList = v, volumeLocationList.Copy()
 				}
 			}
 		}