@Override
  public String toString() {
    return "DiskSpaceRequirements{segmentSizeInBytes=" + segmentSizeInBytes + ", segmentsNeeded=" + segmentsNeeded
        + ", swapSegmentsInUse=" + swapSegmentsInUse + '}';
  }
@return the number of swap segments currently in use by this entity.
ambry-store/src/main/java/com/github/ambry/store/DiskSpaceRequirements.java