public List<String> getAllLocalUnSequenceFileFolders() {
    return unSeqDir2TierLevel.keySet().stream()
        .filter(FSUtils::isLocal)
        .collect(Collectors.toList());
  }
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