code: public void initialize(URI name, Configuration conf) throws IOException {
      this.conf = conf;
      
      // init the codec from conf.
      Codec.initializeCodecs(conf);
  
      Class<?> clazz = conf.getClass("fs.raid.underlyingfs.impl",
          DistributedFileSystem.class);
      if (clazz == null) {
        throw new IOException("No FileSystem for fs.raid.underlyingfs.impl.");
      }
      
      String ignoredDirectories = conf.get(DIRECTORIES_IGNORE_PARITY_CHECKING_KEY);
      if (ignoredDirectories != null && ignoredDirectories.length() > 0) {
        String[] directories = ignoredDirectories.split(",");
        directoriesIgnoreCheckParity = new ArrayList<String>();
        for (String dir : directories) {
          if (dir.length() > 0 && dir.startsWith("/")) {
            if (!dir.endsWith("/")) {
              dir = dir + "/";
            }
            directoriesIgnoreCheckParity.add(dir);
          }
        }
      }
  
      this.fs = (FileSystem)ReflectionUtils.newInstance(clazz, null); 
      super.initialize(name, conf);
    }
docs: /* Initialize a Raid FileSystem