diff --git a/weed/sequence/memory_sequencer.go b/weed/sequence/memory_sequencer.go
index d727dc723..e20c29cc7 100644
--- a/weed/sequence/memory_sequencer.go
+++ b/weed/sequence/memory_sequencer.go
@@ -15,12 +15,12 @@ func NewMemorySequencer() (m *MemorySequencer) {
 	return
 }
 
-func (m *MemorySequencer) NextFileId(count uint64) (uint64, uint64) {
+func (m *MemorySequencer) NextFileId(count uint64) uint64 {
 	m.sequenceLock.Lock()
 	defer m.sequenceLock.Unlock()
 	ret := m.counter
-	m.counter += uint64(count)
-	return ret, count
+	m.counter += count
+	return ret
 }
 
 func (m *MemorySequencer) SetMax(seenValue uint64) {
diff --git a/weed/sequence/sequence.go b/weed/sequence/sequence.go
index fbdc3b8ef..2258d001b 100644
--- a/weed/sequence/sequence.go
+++ b/weed/sequence/sequence.go
@@ -1,7 +1,7 @@
 package sequence
 
 type Sequencer interface {
-	NextFileId(count uint64) (uint64, uint64)
+	NextFileId(count uint64) uint64
 	SetMax(uint64)
 	Peek() uint64
 }
diff --git a/weed/server/master_server_handlers.go b/weed/server/master_server_handlers.go
index c10f9a5b7..9bcd35ced 100644
--- a/weed/server/master_server_handlers.go
+++ b/weed/server/master_server_handlers.go
@@ -65,11 +65,17 @@ func (ms *MasterServer) findVolumeLocation(collection, vid string) operation.Loo
 	var err error
 	if ms.Topo.IsLeader() {
 		volumeId, newVolumeIdErr := needle.NewVolumeId(vid)
-		machines := ms.Topo.Lookup(collection, volumeId)
-		for _, loc := range machines {
-			locations = append(locations, operation.Location{Url: loc.Url(), PublicUrl: loc.PublicUrl})
+		if newVolumeIdErr != nil {
+			err = fmt.Errorf("Unknown volume id %s", vid)
+		} else {
+			machines := ms.Topo.Lookup(collection, volumeId)
+			for _, loc := range machines {
+				locations = append(locations, operation.Location{Url: loc.Url(), PublicUrl: loc.PublicUrl})
+			}
+			if locations == nil {
+				err = fmt.Errorf("volume id %s not found", vid)
+			}
 		}
-		err = newVolumeIdErr
 	} else {
 		machines, getVidLocationsErr := ms.MasterClient.GetVidLocations(vid)
 		for _, loc := range machines {
diff --git a/weed/server/master_server_handlers_admin.go b/weed/server/master_server_handlers_admin.go
index 486bf31f4..a5d976008 100644
--- a/weed/server/master_server_handlers_admin.go
+++ b/weed/server/master_server_handlers_admin.go
@@ -18,9 +18,10 @@ import (
 )
 
 func (ms *MasterServer) collectionDeleteHandler(w http.ResponseWriter, r *http.Request) {
-	collection, ok := ms.Topo.FindCollection(r.FormValue("collection"))
+	collectionName := r.FormValue("collection")
+	collection, ok := ms.Topo.FindCollection(collectionName)
 	if !ok {
-		writeJsonError(w, r, http.StatusBadRequest, fmt.Errorf("collection %s does not exist", r.FormValue("collection")))
+		writeJsonError(w, r, http.StatusBadRequest, fmt.Errorf("collection %s does not exist", collectionName))
 		return
 	}
 	for _, server := range collection.ListVolumeServers() {
@@ -35,7 +36,10 @@ func (ms *MasterServer) collectionDeleteHandler(w http.ResponseWriter, r *http.R
 			return
 		}
 	}
-	ms.Topo.DeleteCollection(r.FormValue("collection"))
+	ms.Topo.DeleteCollection(collectionName)
+
+	w.WriteHeader(http.StatusNoContent)
+	return
 }
 
 func (ms *MasterServer) dirStatusHandler(w http.ResponseWriter, r *http.Request) {
@@ -53,6 +57,7 @@ func (ms *MasterServer) volumeVacuumHandler(w http.ResponseWriter, r *http.Reque
 		gcThreshold, err = strconv.ParseFloat(gcString, 32)
 		if err != nil {
 			glog.V(0).Infof("garbageThreshold %s is not a valid float number: %v", gcString, err)
+			writeJsonError(w, r, http.StatusNotAcceptable, fmt.Errorf("garbageThreshold %s is not a valid float number", gcString))
 			return
 		}
 	}
diff --git a/weed/server/volume_grpc_erasure_coding.go b/weed/server/volume_grpc_erasure_coding.go
index 8140a06f6..242480197 100644
--- a/weed/server/volume_grpc_erasure_coding.go
+++ b/weed/server/volume_grpc_erasure_coding.go
@@ -252,9 +252,14 @@ func (vs *VolumeServer) VolumeEcShardRead(req *volume_server_pb.VolumeEcShardRea
 	startOffset, bytesToRead := req.Offset, req.Size
 
 	for bytesToRead > 0 {
-		bytesread, err := ecShard.ReadAt(buffer, startOffset)
+		// min of bytesToRead and bufSize
+		bufferSize := bufSize
+		if bufferSize > bytesToRead {
+			bufferSize = bytesToRead
+		}
+		bytesread, err := ecShard.ReadAt(buffer[0:bufferSize], startOffset)
 
-		// println(fileName, "read", bytesread, "bytes, with target", bytesToRead)
+		// println("read", ecShard.FileName(), "startOffset", startOffset, bytesread, "bytes, with target", bufferSize)
 		if bytesread > 0 {
 
 			if int64(bytesread) > bytesToRead {
@@ -268,6 +273,7 @@ func (vs *VolumeServer) VolumeEcShardRead(req *volume_server_pb.VolumeEcShardRea
 				return err
 			}
 
+			startOffset += int64(bytesread)
 			bytesToRead -= int64(bytesread)
 
 		}
diff --git a/weed/storage/store.go b/weed/storage/store.go
index f46b77b7b..4d1061bed 100644
--- a/weed/storage/store.go
+++ b/weed/storage/store.go
@@ -165,8 +165,9 @@ func (s *Store) CollectHeartbeat() *master_pb.Heartbeat {
 	var maxFileKey NeedleId
 	collectionVolumeSize := make(map[string]uint64)
 	for _, location := range s.Locations {
+		var deleteVids []needle.VolumeId
 		maxVolumeCount = maxVolumeCount + location.MaxVolumeCount
-		location.Lock()
+		location.RLock()
 		for _, v := range location.volumes {
 			if maxFileKey < v.MaxFileKey() {
 				maxFileKey = v.MaxFileKey()
@@ -175,8 +176,7 @@ func (s *Store) CollectHeartbeat() *master_pb.Heartbeat {
 				volumeMessages = append(volumeMessages, v.ToVolumeInformationMessage())
 			} else {
 				if v.expiredLongEnough(MAX_TTL_VOLUME_REMOVAL_DELAY) {
-					location.deleteVolumeById(v.Id)
-					glog.V(0).Infoln("volume", v.Id, "is deleted.")
+					deleteVids = append(deleteVids, v.Id)
 				} else {
 					glog.V(0).Infoln("volume", v.Id, "is expired.")
 				}
@@ -184,7 +184,17 @@ func (s *Store) CollectHeartbeat() *master_pb.Heartbeat {
 			fileSize, _, _ := v.FileStat()
 			collectionVolumeSize[v.Collection] += fileSize
 		}
-		location.Unlock()
+		location.RUnlock()
+
+		if len(deleteVids) > 0 {
+			// delete expired volumes.
+			location.Lock()
+			for _, vid := range deleteVids {
+				location.deleteVolumeById(vid)
+				glog.V(0).Infoln("volume", vid, "is deleted.")
+			}
+			location.Unlock()
+		}
 	}
 
 	for col, size := range collectionVolumeSize {
diff --git a/weed/storage/store_ec.go b/weed/storage/store_ec.go
index 8271324cf..7e3f1a46c 100644
--- a/weed/storage/store_ec.go
+++ b/weed/storage/store_ec.go
@@ -288,7 +288,7 @@ func (s *Store) readRemoteEcShardInterval(ctx context.Context, sourceDataNodes [
 	}
 
 	for _, sourceDataNode := range sourceDataNodes {
-		glog.V(4).Infof("read remote ec shard %d.%d from %s", vid, shardId, sourceDataNode)
+		glog.V(3).Infof("read remote ec shard %d.%d from %s", vid, shardId, sourceDataNode)
 		n, is_deleted, err = s.doReadRemoteEcShardInterval(ctx, sourceDataNode, needleId, vid, shardId, buf, offset)
 		if err == nil {
 			return
@@ -340,7 +340,7 @@ func (s *Store) doReadRemoteEcShardInterval(ctx context.Context, sourceDataNode
 }
 
 func (s *Store) recoverOneRemoteEcShardInterval(ctx context.Context, needleId types.NeedleId, ecVolume *erasure_coding.EcVolume, shardIdToRecover erasure_coding.ShardId, buf []byte, offset int64) (n int, is_deleted bool, err error) {
-	glog.V(4).Infof("recover ec shard %d.%d from other locations", ecVolume.VolumeId, shardIdToRecover)
+	glog.V(3).Infof("recover ec shard %d.%d from other locations", ecVolume.VolumeId, shardIdToRecover)
 
 	enc, err := reedsolomon.New(erasure_coding.DataShardsCount, erasure_coding.ParityShardsCount)
 	if err != nil {
diff --git a/weed/topology/topology.go b/weed/topology/topology.go
index ea0769248..b7ebe8af5 100644
--- a/weed/topology/topology.go
+++ b/weed/topology/topology.go
@@ -125,7 +125,7 @@ func (t *Topology) PickForWrite(count uint64, option *VolumeGrowOption) (string,
 	if datanodes.Length() == 0 {
 		return "", 0, nil, fmt.Errorf("no writable volumes available for collection:%s replication:%s ttl:%s", option.Collection, option.ReplicaPlacement.String(), option.Ttl.String())
 	}
-	fileId, count := t.Sequence.NextFileId(count)
+	fileId := t.Sequence.NextFileId(count)
 	return needle.NewFileId(*vid, fileId, rand.Uint32()).String(), count, datanodes.Head(), nil
 }
 
diff --git a/weed/topology/topology_map.go b/weed/topology/topology_map.go
index 37a88c9ed..0ad30f12e 100644
--- a/weed/topology/topology_map.go
+++ b/weed/topology/topology_map.go
@@ -23,7 +23,7 @@ func (t *Topology) ToMap() interface{} {
 			}
 		}
 	}
-	m["layouts"] = layouts
+	m["Layouts"] = layouts
 	return m
 }