class DataStorage extends Storage {

  void recoverTransitionRead(DataNode datanode, NamespaceInfo nsInfo,
      Collection<StorageLocation> dataDirs, StartupOption startOpt) throws IOException {
    if (this.initialized) {
      LOG.info("DataNode version: " + HdfsConstants.DATANODE_LAYOUT_VERSION
          + " and NameNode layout version: " + nsInfo.getLayoutVersion());
      this.storageDirs = new ArrayList<StorageDirectory>(dataDirs.size());
      // mark DN storage is initialized
      this.initialized = true;
    }

    if (addStorageLocations(datanode, nsInfo, dataDirs, startOpt).isEmpty()) {
      throw new IOException("All specified directories are failed to load.");
    }
  }

    DataStorage();
  public  DataStorage(StorageInfo storageInfo);

}