class DataStorage extends Storage {

  synchronized void recoverTransitionRead(DataNode datanode,
      NamespaceInfo nsInfo, Collection<StorageLocation> dataDirs,
      StartupOption startOpt)
      throws IOException {
    if (initialized) {
      // DN storage has been initialized, no need to do anything
      return;
    }
    LOG.info("DataNode version: " + HdfsConstants.DATANODE_LAYOUT_VERSION
        + " and NameNode layout version: " + nsInfo.getLayoutVersion());

    this.storageDirs = new ArrayList<StorageDirectory>(dataDirs.size());
    addStorageLocations(datanode, nsInfo, dataDirs, startOpt, true, false);
    
    // mark DN storage is initialized
    this.initialized = true;
  }

    DataStorage();
  public  DataStorage(StorageInfo storageInfo);

}