code: private final void flushBuffer() throws IOException {
  		if (bufOutput.position() > 0) {
  			bufOutput.flip();
  			fcOutput.write(bufOutput);
  			bufOutput.clear();
  			// log.debug("offsetOutputUncommited=" + offsetOutputUncommited + " offsetOutputCommited=" +
  			// offsetOutputCommited + " fcOutput.position()=" + fcOutput.position());
  			offsetOutputUncommited = offsetOutputCommited = fcOutput.position();
  			if (syncOnFlush) {
  				fcOutput.force(false);
  				if (callback != null) {
  					callback.synched(offsetOutputCommited);
  				}
  			}
  		}
  	}
docs: Write uncommited data to disk
  
  @throws IOException