Why not hydrogen?
@handle, I have not seen a drive where all the heads are not rigidly mounted together (so they are on a different platter but reading the same track.) MB/sec can increase, but random access times do not.
@Jim O'Reilly, yes those who choose SSDs do it because the IOPs matter. Well, for some purposes the cost per GB for SSD is far too high, and the storage capacity far too low. SSD is close to an order of magnitude more expensive than a hard disk after all.
@AC re "Price of helium?", in actuality, the US strategic helium reserve has been ordered to be sold off between 2005 and 2014 -- a reserve built up over the course of about 70 years (originally for blimps) being sold off in 9 years. This has caused other helium production to stop -- the natural gas refineries have helium as a "waste" gas, which was filtered and collected, but now is vented into the atmosphere never to be seen again. The prediction with current production and use rates is that in 20 years a balloons worth of helium would cost like $100, and it'd run out in 25 years. Yeah, that'd drive up the cost of a helium-filled hard drive 8-).
I wonder why not use hydrogen? I would not think a hard drive would hold enough for a titanic situation to be too likely after all, and production would be quite easy of course.