Solid-state drives are all the rage with laptops like the Macbook Air and its Ultrabook rivals utilising them for their speed and battery-saving features. But capacities are still limited and prices much higher than slower traditional hard drives.

Seagate offers a middle way with its Momentus XT hybrid drive – mixing solid-state memory with the traditional spinning platter – and has sold 1m of the drives since it came up with the new category last year (the company says its 2007 Momentus PSD drive doesn’t really count).