Since before buying reigned a real GB of storage shortage and the other 2 plates were full, had a new forth! And I have decided on the WD My Book hard drive in the 2TB version. It is as a backup disk for my 27 "iMac in use and running as soon as a Time Machine backup must be done / should.
So far, it does what it is supposed muck without any. Hope, of course, they do not give up the ghost.