code: private void initStandbyFS() {
      lastStandbyFSInit = System.currentTimeMillis();
      try {
        if (standbyFS != null) {
          standbyFS.close();
        }
  
        LOG.info("DAFS initializing standbyFS");
        LOG.info("DAFS primary=" + primaryURI.toString() +
                 " standby=" + standbyURI.toString());
        standbyFS = new StandbyFS();
        standbyFS.initialize(standbyURI, conf);
  
      } catch (Exception e) {
        LOG.info("DAFS cannot initialize standbyFS: " +
                 StringUtils.stringifyException(e));
        standbyFS = null;
      }
    }
docs: Try to initialize standbyFS. Must hold writelock to call this method.