Hard Disk Drive Capacity at High Magnetic Areal Density

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Abstract
Increases in recording areal density have propelled the disk drive industry in the last dozen years. Several studies and research programs strive to accomplish an areal density of 1 Tb/in/sup 2/. At present, the future of the hard disk drive technology appears predicated on monotonic and unbound areal density growth. The system consequences of using large areal densities are the subject of this paper. It is argued that the limited signal-to-noise ratio (SNR) predicted at 1 Tb/in/sup 2/, as well as the extreme mechanical demands on the system, will cause the user capacity not to grow linearly with areal density, as has been the case in the past. This is due, among other reasons, to the increased servo overhead, the increased error-correction code overhead, and the mechanical requirements that compel the reduction of the size of the mechanism. Without casting in doubt the feasibility of magnetic bit recording at 1 Tb/in/sup 2/, scaling laws nevertheless show that there may be limited rewards for the technical efforts directed toward accomplishing 1 Tb/in/sup 2/. Unless the system SNR can be maintained at about 18 dB, areal density gains will not result in proportional user-capacity gains.