skip already loaded backends

weed/storage/backend/backend.go

@@ -58,6 +58,9 @@ func LoadConfiguration(config *util.ViperProxy) {
 			if !config.GetBool(StorageBackendPrefix + "." + backendTypeName + "." + backendStorageId + ".enabled") {
 				continue
 			}
+			if _, found := BackendStorages[backendTypeName+"."+backendStorageId]; found {
+				continue
+			}
 			backendStorage, buildErr := backendStorageFactory.BuildStorage(config,
 				StorageBackendPrefix+"."+backendTypeName+"."+backendStorageId+".", backendStorageId)
 			if buildErr != nil {
@@ -81,6 +84,9 @@ func LoadFromPbStorageBackends(storageBackends []*master_pb.StorageBackend) {
 			glog.Warningf("storage type %s not found", storageBackend.Type)
 			continue
 		}
+		if _, found := BackendStorages[storageBackend.Type+"."+storageBackend.Id]; found {
+			continue
+		}
 		backendStorage, buildErr := backendStorageFactory.BuildStorage(newProperties(storageBackend.Properties), "", storageBackend.Id)
 		if buildErr != nil {
 			glog.Fatalf("fail to create backend storage %s.%s", storageBackend.Type, storageBackend.Id)