public long countRegionDiskSize() {
    AtomicLong diskSize = new AtomicLong(0);
    TierManager.getInstance()
        .getAllLocalFilesFolders()
        .forEach(
            folder -> {
              folder = folder + File.separator + databaseName + File.separator + dataRegionId;
              countFolderDiskSize(folder, diskSize);
            });
    return diskSize.get() / 1024 / 1024;
  }
@return the disk space occupied by this data region, unit is MB
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/DataRegion.java