code: public void updateUsedBytes(Map<String, Long> usedBytesOnTiers) {
      mUsedBytes = 0;
      mUsedBytesOnTiers = new HashMap<>(usedBytesOnTiers);
      for (long t : mUsedBytesOnTiers.values()) {
        mUsedBytes += t;
      }
    }
docs: Sets the used space of the worker in bytes.
  
  @param usedBytesOnTiers used bytes on each storage tier