Industry divided over future of hard drives
Published: 29 Aug 2006 13:25 BST
Heat or dots? The question is dividing the hard drive industry as it prepares for a major product overhaul.
Perpendicular hard drive technology, which started appearing last year, currently lets manufacturers increase drive density, or the amount of data stored, by around 50 percent annually. But that pace of progress is likely to sputter in about four to five years.
To keep progress going, the first disks based on new technology will need to enter the market around 2011. Competitors differ, however, on how and when ideas for revamping drives should become reality.
Seagate Technologies, the world's largest drive maker, wants first to adopt a concept called "heat-assisted magnetic recording". This involves heating microscopic cells on the disk platters as part of the recording process.
Meanwhile, Hitachi Global Storage Technologies, number two in the industry, favours proceeding with something called "patterned media". In this technique, the cells that store data which now sit next to each other in a continuous film would be isolated from each other like dots.
Time is of the essence: Five years from concept to the first finished products that can be shipped to customers isn't long. Additionally, Flash memory makers assert that their chips will start to displace drives in notebooks over the coming years. Drive makers scoff at the notion, but agree that technological changes need to occur for drives to protect their turf.
"We need to maintain that 40 percent areal-density growth rate, at a minimum, to stay ahead of flash, and we are dang well going to do it," said Mark Kryder, chief technology officer at Seagate.
Eventually, manufacturers will combine heat-assisted and patterned media to produce drives that will be capable of storing 50 to 100 terabits of data per square inch. That's 280 to 560 times denser than the 178.8Gb-per-square-inch drive coming from Toshiba later this year. (A square inch of 100-terabit material could hold as much data as 12,500 pickup trucks filled with books.)
Seagate and Hitachi, as well as other drive makers, are experimenting with both technologies in their labs. Still, the next step is yet to be determined.
"Most people have thought heat assistance probably would be first, but who knows?" said Jim Porter, president of Disk/Trend, which analyses the disk drive industry.
Superparamagneticexpialidocious
The enemy of hard drives is your thermostat. The devices store data in bits, which are microscopic spots on a hard drive platter. The bits themselves are made up of about 50 to 100 cobalt-platinum grains. When the grains get magnetised in a particular direction, the bit represents either a "1" or "0".
To increase the areal density, which is the amount of data a single platter inside a hard drive can hold, engineers have shrunk the size of bits and grains over the years. This has helped PC makers to boost the capacity of hard drives from a few megabytes to more than 100GB.
Successive years of shrinkage, however, have led to magnetic grains that measure about 8nm long. (A nanometre is a billionth of a metre.)
Reducing the grains further in size could cause them to flip at room temperature and so corrupt the data an aspect of the "superparamagnetic effect", first identified in the mid-1990s by Stan Charap of Carnegie Mellon University. And cutting back on the number of grains inside each bit, absent further changes, would increase noise and lower reliability.
Drive manufacturers have bought time with perpendicular drives, which stack the bits vertically. But that solution doesn't eliminate the "no more shrinkage" problem.
One or the other
The heat-assisted camp wants to change the grains. Unlike cobalt-platinum grains, iron-platinum grains will not flip at room temperature, Kryder said. To record or erase data, a laser integrated into the drive would heat a particular bit. The data would get recorded or erased, and the bit would quickly cool.
"We'd have to change the (recording) head to add heat, but it's not that big a deal," Kryder said. Adding a laser wouldn't increase costs much, he noted. More importantly, the bits could be applied to the platter surfaces through a film, which is how bits are applied today.
Material changes, however, are rarely easy; for example, the switch from aluminium to copper in semiconductors confounded semiconductor makers. For the heat-applied technology, engineers would have to perfect ways to pinpoint the heat from the laser.
"It requires small optical spots. It requires very sharp thermal gradients. It requires new materials," John Best, chief technologist at Hitachi, said, pointing out hurdles in the process.
"You could argue (about) which one's easier to solve, but it looked to us that the practical problems with patterned media meant that we could probably do it first more easily," Best added.
By contrast, the patterned media group wants to keep the current grains. It proposes, instead, reducing the number of grains in each bit from 100 to one, and then isolating the bits from each other
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