private String getBackupDirName(DiskStoreImpl diskStore) {
    String name = diskStore.getName();

    if (name == null) {
      name = GemFireCacheImpl.getDefaultDiskStoreName();
    }

    return name + "_" + diskStore.getDiskStoreID().toString();
  }
Returns the dir name used to back up this DiskStore's directories under. The name is a
concatenation of the disk store name and id.
geode-core/src/main/java/org/apache/geode/internal/cache/backup/FileSystemBackupWriter.java