The next generation of disk drives will hammer users because they will be too expensive according to IBM's green CTO, Steve Bowden.
Speaking at the Carbon Footprint IT summit in London he said that the current trend in increasing disk drive data density is unsustainable. This is because the platter surface material would be very expensive.
Currently disk drives use perpendicular recording in which magnetised areas, previously laid out longitudinally on disk, have been flipped so as to be upright and have their lower extremity deep below the recording material's surface. This means that their upper part, forming the magnetised bit area on the platter surface, is small and the bits can be packed more closely together.
The next step is generally reckoned to involve heat-assisted magnetic recording or HAMR and has an even tinier area of the surface momentarily heated by a laser before the magnetic charge is applied. It means, hopefully, increased data density with the magnetic charge 'baked' in to the media surface.
Bowden seems to be saying that the development and production costs for the media coating material involved will be so high as to make the disks far less affordable than currently. Ergo we need to move to tiered storage and transfer less valuable data to the appropriately-priced storage tier.