code: @AfterBatch
    public void afterBatch()
    {
      long requestSequence = _requestSequence;
      
      if (! _isFsync) {
        return;
      }
      
      _isFsync = false;
      
      try {
        _storeFsync.fsync();
        /*
        if (_tailSequence < requestSequence) {
          _storeFsync.fsync();
        }
        */
      } catch (Throwable e) {
        e.printStackTrace();
      } finally {
        _tailSequence = requestSequence;
      }
    }
docs: Completes any fsyncs in a batch.
  
  Because the fsync is slow, this method will typically block while
  new requests fill the queue, making the next batch efficient.