Desktop hard drive capacities will have quadrupled from today's 1TB to 4TB in four years, if the plans of Hitachi's storage arm—Hitachi Global Storage Technologies—come to fruition. As CNet reports, the advance will result from the introduction of a new kind of drive head dubbed current perpendicular-to-the-plane giant magneto-resistive, or CPP-GMR for short. CNet explains:
The CPP-GMR drive essentially changes the structure of drive heads. Current drives come with a tunnel magnetoresistance head. In these, an insulating layer sits between two magnetic layers. Electrons can tunnel through the layer. Precisely controlling the tunneling ultimately results in the 1s and 0s of data.
Unfortunately, drive heads need to be shrunk as areal density . . . increases. Shrinking the heads increases electrical resistance, which in turn creates electrical noise and potential degradation in performance. Past 500 gigabits per square inch of areal density, TMR heads may not work reliably. (Current top-end drives exhibit an areal density of around 200 gigabits per square inch.)
In a CPP-GMR head, the insulator is eliminated and replaced by a conductor, usually copper. Instead of running parallel with the middle layer, the current runs at a perpendicular angle. The structure reduces resistance and thus allows the head to be shrunk.
To put the above into more concrete terms, CNet says current TMR heads can read media with tracks 70nm apart from each other. Tracks should be able to shrink to 50nm in 2009 and to just 30nm in 2011 thanks to CPP-GMR heads.
The first commercial hard drives to employ CPP-GMR heads are expected to become available in either 2009 or 2010.