diff --git a/weed/server/filer_server_handlers_write_autochunk.go b/weed/server/filer_server_handlers_write_autochunk.go
index 2bd1104d3..237f121fe 100644
--- a/weed/server/filer_server_handlers_write_autochunk.go
+++ b/weed/server/filer_server_handlers_write_autochunk.go
@@ -121,14 +121,11 @@ func (fs *FilerServer) doPutAutoChunk(ctx context.Context, w http.ResponseWriter
 	return
 }
 
-func (fs *FilerServer) saveMetaData(ctx context.Context, r *http.Request, fileName string, contentType string, so *operation.StorageOption, md5bytes []byte, fileChunks []*filer_pb.FileChunk, chunkOffset int64, content []byte) (filerResult *FilerPostResult, replyerr error) {
+func isAppend(r *http.Request) bool {
+	return r.URL.Query().Get("op") == "append"
+}
 
-	// maybe compact chunks
-	fileChunks, replyerr = filer.MaybeManifestize(fs.saveAsChunk(so), fileChunks)
-	if replyerr != nil {
-		glog.V(0).Infof("manifestize %s: %v", r.RequestURI, replyerr)
-		return
-	}
+func (fs *FilerServer) saveMetaData(ctx context.Context, r *http.Request, fileName string, contentType string, so *operation.StorageOption, md5bytes []byte, fileChunks []*filer_pb.FileChunk, chunkOffset int64, content []byte) (filerResult *FilerPostResult, replyerr error) {
 
 	// detect file mode
 	modeStr := r.URL.Query().Get("mode")
@@ -149,25 +146,61 @@ func (fs *FilerServer) saveMetaData(ctx context.Context, r *http.Request, fileNa
 		}
 	}
 
-	glog.V(4).Infoln("saving", path)
-	entry := &filer.Entry{
-		FullPath: util.FullPath(path),
-		Attr: filer.Attr{
-			Mtime:       time.Now(),
-			Crtime:      time.Now(),
-			Mode:        os.FileMode(mode),
-			Uid:         OS_UID,
-			Gid:         OS_GID,
-			Replication: so.Replication,
-			Collection:  so.Collection,
-			TtlSec:      so.TtlSeconds,
-			Mime:        contentType,
-			Md5:         md5bytes,
-			FileSize:    uint64(chunkOffset),
-		},
-		Chunks:  fileChunks,
-		Content: content,
+	var entry *filer.Entry
+	var mergedChunks []*filer_pb.FileChunk
+	// when it is an append
+	if isAppend(r) {
+		existingEntry, findErr := fs.filer.FindEntry(ctx, util.FullPath(path))
+		if findErr != nil && findErr != filer_pb.ErrNotFound {
+			glog.V(0).Infof("failing to find %s: %v", path, findErr)
+		}
+		entry = existingEntry
 	}
+	if entry != nil {
+		entry.Mtime = time.Now()
+		entry.Md5 = nil
+		// adjust chunk offsets
+		for _, chunk := range fileChunks {
+			chunk.Offset += int64(entry.FileSize)
+		}
+		mergedChunks = append(entry.Chunks, fileChunks...)
+		entry.FileSize += uint64(chunkOffset)
+
+		// TODO
+		if len(entry.Content) > 0 {
+			replyerr = fmt.Errorf("append to small file is not supported yet")
+			return
+		}
+
+	} else {
+		glog.V(4).Infoln("saving", path)
+		mergedChunks = fileChunks
+		entry = &filer.Entry{
+			FullPath: util.FullPath(path),
+			Attr: filer.Attr{
+				Mtime:       time.Now(),
+				Crtime:      time.Now(),
+				Mode:        os.FileMode(mode),
+				Uid:         OS_UID,
+				Gid:         OS_GID,
+				Replication: so.Replication,
+				Collection:  so.Collection,
+				TtlSec:      so.TtlSeconds,
+				Mime:        contentType,
+				Md5:         md5bytes,
+				FileSize:    uint64(chunkOffset),
+			},
+			Content: content,
+		}
+	}
+
+	// maybe compact entry chunks
+	mergedChunks, replyerr = filer.MaybeManifestize(fs.saveAsChunk(so), mergedChunks)
+	if replyerr != nil {
+		glog.V(0).Infof("manifestize %s: %v", r.RequestURI, replyerr)
+		return
+	}
+	entry.Chunks = mergedChunks
 
 	filerResult = &FilerPostResult{
 		Name: fileName,
@@ -187,7 +220,7 @@ func (fs *FilerServer) saveMetaData(ctx context.Context, r *http.Request, fileNa
 	}
 
 	if dbErr := fs.filer.CreateEntry(ctx, entry, false, false, nil); dbErr != nil {
-		fs.filer.DeleteChunks(entry.Chunks)
+		fs.filer.DeleteChunks(fileChunks)
 		replyerr = dbErr
 		filerResult.Error = dbErr.Error()
 		glog.V(0).Infof("failing to write %s to filer server : %v", path, dbErr)
@@ -211,7 +244,7 @@ func (fs *FilerServer) uploadReaderToChunks(w http.ResponseWriter, r *http.Reque
 		if err != nil {
 			return nil, nil, 0, err, nil
 		}
-		if chunkOffset == 0 {
+		if chunkOffset == 0 && !isAppend(r) {
 			if len(data) < fs.option.SaveToFilerLimit || strings.HasPrefix(r.URL.Path, filer.DirectoryEtcRoot) && len(data) < 4*1024 {
 				smallContent = data
 				chunkOffset += int64(len(data))