The new 3TB Ironwolf ( ST3000VN006) has 2 platters and it will replace the older 3 platter part number ( ST3000VN008).
Having one less platter means that ST3000VN006 is lighter and has better engery efficiency ( even if only marginally ). Transfer rates of new part number are up from 180 MB/s of earlier one to 202 MB/s.