Some use the HDD as backup, I am about to replace 2, 2TB drives in main system, both @ 99% Capacity, with 4TB drive's, the 2, 2TB will go the shelf, as the backup to new drives once backup has been achieved, they will gather dust (in plastic box) with the original backup 1TB's & "those that came before it". So any "retrieval" is plugging a HHD in, this of course, can gather speed over time, & so I have a 80 litre plastic tub full of previous HDD ...
However I think SSD is next cab on rank as far as HDD goes, 8TB? Nova-chips 8TB's sound fine but, cost is always issue. As I know 4TB all flash PCI card based are still around $20000, always things evolve, but a permanent solution is still ahead ...
( HGST FlashMAX II 4.8TB PCIe Enterprise SSD HVFM24848AHP200 $23866.98)
Some are trying ..
5D ‘Superman memory’ crystal could lead to unlimited lifetime data storage
http://www.southampton.ac.uk/mediacentre/news/2013/jul/13_131.shtml
Biting the hand that feeds IT
