Despite the focus on immediate storage is on the solid-state drive, whenever a large backup is needed then the mechanical hard-disk drive is still reigning supreme, and the demand for data density has never been higher. In the consumer space 4TB drives have been on sale for a while, currently for around $164 in the US or 123 in the UK. These were four platters at 1TB each, or five platters at 800 GB each, using PMR (perpendicular magnetic recording, remember this video?).