private void shutdownTimedService(ScheduledExecutorService pool, String poolName) {
    if (pool != null) {
      pool.shutdownNow();
      try {
        pool.awaitTermination(30, TimeUnit.SECONDS);
      } catch (InterruptedException e) {
        LOGGER.warn("{} still doesn't exit after 30s", poolName);
        Thread.currentThread().interrupt();
      }
    }
  }
get StorageGroup -> DataRegionIdList map from data/system directory.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/StorageEngine.java