public static File getDataRegionSystemDir(String dataBaseName, String dataRegionId) {
    return SystemFileFactory.INSTANCE.getFile(
        systemDir + File.separator + dataBaseName, dataRegionId);
  }
reboot timed flush sequence/unsequence memtable thread
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/StorageEngine.java