This can be different from the designated replication factor of the file
   * because the namenode does not maintain replication for the blocks which are
   * currently being written to. Depending on the configuration, the client may
   * continue to write to a block even if a few datanodes in the write pipeline
   * have failed, or the client may add a new datanodes once a datanode has
   * failed.
This can be different from the designated replication factor of the file
   * because the namenode does not maintain replication for the blocks which are
   * currently being written to. Depending on the configuration, the client may
   * continue to write to a block even if a few datanodes in the write pipeline
   * have failed, or the client may add a new datanodes once a datanode has
   * failed. | HdfsDataOutputStream.java