@Override
 public void toData(DataOutput out) throws IOException {
   super.toData(out);
   SerializationHelper.writeServerLocationSet(this.excludedServers, out);
 }
 @Override
 public void fromData(DataInput in) throws IOException, ClassNotFoundException {
   super.fromData(in);
   this.excludedServers = SerializationHelper.readServerLocationSet(in);
 }