 @param favoredNodes datanodes that should be favored as targets. This
   *          is only a hint and due to cluster state, namenode may not be 
   *          able to place the blocks on these datanodes.
 @param favoredNodes datanodes that should be favored as targets. This
   *          is only a hint and due to cluster state, namenode may not be 
   *          able to place the blocks on these datanodes. | BlockPlacementPolicy.java