public synchronized void resetFolders() {
    long startTime = System.currentTimeMillis();
    seqTiers.clear();
    unSeqTiers.clear();
    seqDir2TierLevel.clear();
    unSeqDir2TierLevel.clear();

    initFolders();
    long endTime = System.currentTimeMillis();
    logger.info("The folders is reset successfully, which takes {} ms.", (endTime - startTime));
  }
total space of each tier, Long.MAX_VALUE when one tier contains remote storage
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/rescon/disk/TierManager.java