While SSDs keep getting cheaper by the day, the price of mechanical storage seems to be declining at a much slower pace. Part of that is no doubt due to last year's floods in Thailand. 2TB and 3TB "Green" hard drives still cost about as much as they did a year ago, and good luck finding a higher-capacity drive with a reasonable price tag.
A recent report by iSuppli puts things in perspective, though. The research firm points out that areal densities have increased quite a bit in the past couple of years, and they're expected to more than double within the next four years or so:
HDD areal densities measuring data-storage capacities are projected to climb to a maximum 1,800 Gigabits (Gb) per square inch per platter by 2016, up from 744 Gb per square inch in 2011, as shown in the figure below. This means that from 2011 to 2016, the five-year compound annual growth rate (CAGR) for HDD areal densities will be equivalent to 19 percent. For this year, HDD areal densities are estimated to reach 780 Gb per square inch per platter, and then rise to 900 Gb per square inch next year.
For reference, iSuppli says an areal density of 625 Gb per square inch works out to about 1TB per platter in a 3.5" desktop hard drive. 5TB hard drives featuring platters with that density "could be available on the market later this year," the research firm adds. Using that same math and the firm's other predictions, one would expect 3.5" drives with capacities around 14TB in 2016, and perhaps 7TB drives as early as next year.
With high-definition video becoming ever more ubiquitous, the higher capacities will no doubt be welcome. Of course, given how much data a single drive will be able to hold, I'll probably feel safer setting up two of them in a RAID-1 array. Losing 14TB to a single mechanical failure can't be good.