Western Digital's HGST division has released the world's first helium-filled 10TB hard drive for everyday use—assuming you have about £600 burning a hole in your pocket, anyway. Meanwhile, despite reiterating that it would have a 10TB drive on the market this year, Seagate hasn't yet moved past the 8TB mark.
The Ultrastar He10 is notable for two reasons: it's hermetically sealed and filled with helium, which is still a rather novel idea; and it has seven platters crammed into a standard-height 25.4mm (1-inch) hard drive.
The platters themselves are impressive, too: instead of using shingled magnetic recording (SMR) to boost areal density, these platters use conventional perpendicular magnetic recording (PMR). PMR has been the standard hard drive recording tech since 2005, when it replaced longitudinal recording. The move to PMR has increased the maximum platter density by an order of magnitude—from about 100Gb per square inch to 1000Gb—but now, alas, we're beginning to hit the limits of PMR.