private void preemptiveSync(final ProtobufLogWriter nextWriter) {
    long startTimeNanos = System.nanoTime();
    try {
      nextWriter.sync(useHsync);
      postSync(System.nanoTime() - startTimeNanos, 0);
    } catch (IOException e) {
      // optimization failed, no need to abort here.
      LOG.warn("pre-sync failed but an optimization so keep going", e);
    }
  }
Run a sync after opening to set up the pipeline.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/FSHLog.java