Tape Areal Density Growth To Outpace Disks and Flash?
November 28, 2011 Timothy Prickett Morgan
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A lot of people want tapes and disks to die and flash to take over, but it looks like tape technology is not about to go gently into that night. And it is not just a matter of cost per gigabyte, but the density of the three different types of storage devices. Roger Luethy, a storage specialist at IBM Switzerland, posted a paper that storage techies Robert Fontana, Steven Hetzler, and Gary Decad of the Almaden Research Center in San Jose, California, published some time earlier this year that shows that maybe the 40 percent annual growth rate in areal density (in terms of gigabytes per square inch) will be maintained or even doubled up for tape technology, and that the growth rate in disk drive and flash storage density could be cut in half. According to the IBM research paper, which you can read here, this is what the trend lines would look like if current trends in storage media density would persist into the future:
Everything looks hunky dory, right? Tape has nowhere the density of disk or flash. I would remind you that back in 2000, Intel was projecting with absolute confidence that we would be breaking the 10 GHz speed barrier on chips. Right up until the point where we ran up against the thermal limits of Moore’s Law, which said that you could shrink the size of transistors every 18 months or so. Those same limits of physics that plague processors in one way make it tough on increasing areal density and therefore storage capacity on various magnetic media. So here is what IBM is now projecting as a more likely scenario:
The cut and dry of it is that the bit cell size on tape is anywhere from 300 to 500 times larger than those used in disks and flash, and therefore has more room to shrink. What this means from a practical standpoint is that by 2014, tape technology with maybe 12 Gbit per square inch of areal density could cram as much as 15 TB of capacity into a cartridge, while a disk drive might only come in at 6 TB instead of the 12 TB extrapolation might expect based on historical 40 percent annual growth rate in density. And a flash-based solid state drives might only top out at 1.2 TB by 2014 instead of 2 TB. Obviously, flash, with an access time of microsecond, and disk, with an access time of milliseconds, beats out tape, which takes seconds to find a file (and that is under the best of circumstances). But in 2010, IBM’s researchers remind us, flash cost $3 per GB compared to 3 cents per GB for tape. Everything has its place, and even if you don’t store you data on tape somewhere, you very likely will offload the job to some third party–and one that calls themselves a “cloud” just to be cool.
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