code: public static String getWorkerDataDirectory(String storageDir, AlluxioConfiguration conf) {
      return PathUtils.concatPath(
          storageDir.trim(), conf.get(PropertyKey.WORKER_DATA_FOLDER));
    }
docs: @param storageDir the root of a storage directory in tiered storage
  @param conf Alluxio's current configuration
  
  @return the worker data folder path after each storage directory, the final path will be like
  "/mnt/ramdisk/alluxioworker" for storage dir "/mnt/ramdisk" by appending
  {@link PropertyKey#WORKER_DATA_FOLDER).