diff --git a/weed/server/volume_server_handlers_read.go b/weed/server/volume_server_handlers_read.go
index 9604e7fe8..2db46ac9b 100644
--- a/weed/server/volume_server_handlers_read.go
+++ b/weed/server/volume_server_handlers_read.go
@@ -93,7 +93,7 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 	} else if hasEcVolume {
 		count, err = vs.store.ReadEcShardNeedle(volumeId, n)
 	}
-	if err != nil && err != storage.ErrDeleted && r.FormValue("type") != "replicate" && hasVolume {
+	if err != nil && err != storage.ErrorDeleted && r.FormValue("type") != "replicate" && hasVolume {
 		glog.V(4).Infof("read needle: %v", err)
 		// start to fix it from other replicas, if not deleted and hasVolume and is not a replicated request
 	}
diff --git a/weed/storage/store_ec.go b/weed/storage/store_ec.go
index 55b9a6fc6..a9b6a8ff3 100644
--- a/weed/storage/store_ec.go
+++ b/weed/storage/store_ec.go
@@ -130,7 +130,7 @@ func (s *Store) ReadEcShardNeedle(vid needle.VolumeId, n *needle.Needle) (int, e
 				return 0, fmt.Errorf("locate in local ec volume: %v", err)
 			}
 			if size.IsDeleted() {
-				return 0, ErrDeleted
+				return 0, ErrorDeleted
 			}
 
 			glog.V(3).Infof("read ec volume %d offset %d size %d intervals:%+v", vid, offset.ToActualOffset(), size, intervals)
@@ -143,7 +143,7 @@ func (s *Store) ReadEcShardNeedle(vid needle.VolumeId, n *needle.Needle) (int, e
 				return 0, fmt.Errorf("ReadEcShardIntervals: %v", err)
 			}
 			if isDeleted {
-				return 0, ErrDeleted
+				return 0, ErrorDeleted
 			}
 
 			err = n.ReadBytes(bytes, offset.ToActualOffset(), size, localEcVolume.Version)
diff --git a/weed/storage/volume_checking.go b/weed/storage/volume_checking.go
index f6e75a07c..b76933083 100644
--- a/weed/storage/volume_checking.go
+++ b/weed/storage/volume_checking.go
@@ -30,7 +30,7 @@ func CheckAndFixVolumeDataIntegrity(v *Volume, indexFile *os.File) (lastAppendAt
 			healthyIndexSize = indexSize - int64(i)*NeedleMapEntrySize
 			continue
 		}
-		if err != ErrSizeMismatch {
+		if err != ErrorSizeMismatch {
 			break
 		}
 	}
@@ -94,7 +94,7 @@ func verifyNeedleIntegrity(datFile backend.BackendStorageFile, v needle.Version,
 		return 0, fmt.Errorf("read %s at %d", datFile.Name(), offset)
 	}
 	if n.Size != size {
-		return 0, ErrSizeMismatch
+		return 0, ErrorSizeMismatch
 	}
 	if v == needle.Version3 {
 		bytes := make([]byte, TimestampSize)
diff --git a/weed/storage/volume_read_write.go b/weed/storage/volume_read_write.go
index 7076e198b..cbad4529b 100644
--- a/weed/storage/volume_read_write.go
+++ b/weed/storage/volume_read_write.go
@@ -15,9 +15,9 @@ import (
 	. "github.com/chrislusf/seaweedfs/weed/storage/types"
 )
 
-var ErrNotFound = errors.New("not found")
-var ErrDeleted = errors.New("already deleted")
-var ErrSizeMismatch = errors.New("size mismatch")
+var ErrorNotFound = errors.New("not found")
+var ErrorDeleted = errors.New("already deleted")
+var ErrorSizeMismatch = errors.New("size mismatch")
 
 func (v *Volume) checkReadWriteError(err error) {
 	if err == nil {
@@ -289,7 +289,7 @@ func (v *Volume) readNeedle(n *needle.Needle, readOption *ReadOption) (int, erro
 
 	nv, ok := v.nm.Get(n.Id)
 	if !ok || nv.Offset.IsZero() {
-		return -1, ErrNotFound
+		return -1, ErrorNotFound
 	}
 	readSize := nv.Size
 	if readSize.IsDeleted() {
@@ -297,7 +297,7 @@ func (v *Volume) readNeedle(n *needle.Needle, readOption *ReadOption) (int, erro
 			glog.V(3).Infof("reading deleted %s", n.String())
 			readSize = -readSize
 		} else {
-			return -1, ErrDeleted
+			return -1, ErrorDeleted
 		}
 	}
 	if readSize == 0 {
@@ -327,7 +327,7 @@ func (v *Volume) readNeedle(n *needle.Needle, readOption *ReadOption) (int, erro
 	if time.Now().Before(time.Unix(0, int64(n.AppendAtNs)).Add(time.Duration(ttlMinutes) * time.Minute)) {
 		return bytesRead, nil
 	}
-	return -1, ErrNotFound
+	return -1, ErrorNotFound
 }
 
 func (v *Volume) startWorker() {
diff --git a/weed/util/chunk_cache/chunk_cache_on_disk.go b/weed/util/chunk_cache/chunk_cache_on_disk.go
index c9f7356d6..d724e925e 100644
--- a/weed/util/chunk_cache/chunk_cache_on_disk.go
+++ b/weed/util/chunk_cache/chunk_cache_on_disk.go
@@ -104,7 +104,7 @@ func (v *ChunkCacheVolume) GetNeedle(key types.NeedleId) ([]byte, error) {
 
 	nv, ok := v.nm.Get(key)
 	if !ok {
-		return nil, storage.ErrNotFound
+		return nil, storage.ErrorNotFound
 	}
 	data := make([]byte, nv.Size)
 	if readSize, readErr := v.DataBackend.ReadAt(data, nv.Offset.ToActualOffset()); readErr != nil {
diff --git a/weed/util/chunk_cache/on_disk_cache_layer.go b/weed/util/chunk_cache/on_disk_cache_layer.go
index 2e8f998f7..eebd89798 100644
--- a/weed/util/chunk_cache/on_disk_cache_layer.go
+++ b/weed/util/chunk_cache/on_disk_cache_layer.go
@@ -66,7 +66,7 @@ func (c *OnDiskCacheLayer) getChunk(needleId types.NeedleId) (data []byte) {
 
 	for _, diskCache := range c.diskCaches {
 		data, err = diskCache.GetNeedle(needleId)
-		if err == storage.ErrNotFound {
+		if err == storage.ErrorNotFound {
 			continue
 		}
 		if err != nil {