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The rise of the ultra-dense array
Higher disk densities and smaller form factors will affect power and performance.
EVEN IF BUSINESS demands haven't driven you to classify data and implement tiered storage, changes in technology and relentless data growth will force you to consider these initiatives. Ever-higher data density on disk platters will slow performance, just as applications demand more. To maintain performance, we'll soon have ultra-dense arrays with massive numbers of tiny drive mechanisms that guzzle power and spew heat. It will end only when we get real about data requirements and force the bulk of our storage onto big, slow, efficient drives. Tiered storage is coming whether we like it or not.
Packing more into less
Data is growing at an alarming rate. It's certainly compounding, and some recent studies suggest the growth rate is accelerating. So far, disk capacities have kept up with the growth of space usage, even outpacing Moore's Law. In a past column (see "Five axioms for storage," Storage, June 2004), I noted that while disk capacity isn't necessarily subject to the same technical improvements that inspired Moore's Law, it has kept pace since the mid-1990s, doubling every 18 months. Will this pace continue? I think so.
Until now, the only way to pack more bits onto a disk platter (or ribbon of tape) was to make them smaller and squeeze them in like tinier and tinier puzzle pieces. The big idea of the 1990s that enabled disk storage to jump from 25% to 60% cumulative annual growth was magneto-resistive heads, which allowed much smaller bits to be written. Today's big idea is perpendicular recording. The name refers to the idea of standing magnetic regions (and thus bits) vertically (perpendicular to the surface of the disk) instead of laying them out flat. Current estimates suggest this will increase disk density by a factor of 10.
Although invented in 1976, the first application of perpendicular recording came just this year in the form of a 160GB 2.5-inch disk drive from Seagate. Hitachi Data Systems also plans to introduce the technology, promising 20GB Microdrives and a 1TB 3.5-inch mechanism. It's clear that perpendicular recording will enable at least a few more years of capacity, so what's the problem?
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