'Perpendicular recording' to boost hard drive capacity


By Will Knight The next generation of personal computers and portable music players could hold 10 times more information than current models, thanks to a different way of writing magnetic data to a hard disc. Japanese electronics company Hitachi announced on Monday that a number of its employees had begun testing the experimental technology, known as “perpendicular recording”. The company aims to offer drives incorporating it to the public towards the end of 2005. Hard drives store information by magnetising sectors of a disc in a specific direction, which then correspond to either a “1” or a “0”. This is done by passing magnetic heads over the disc surface which magnetises the sectors in a direction parallel to its surface – so-called “longitudinal recording”. The heads are turned around to impart the reverse polarity. Perpendicular recording uses different-shaped heads to magnetise disc sectors so that the polarity points either up or down – at 90° to the disc’s surface. Data can still be retrieved from the disc in the traditional way, using another head to detect the magnetic charge. “It’s a major technical change,” says John Fox, business manager for Hitachi’s European hard drive business. “But it’s transparent to the user.” Fox told New Scientist that the next five years could see the technology increase the capacity of hard drives by a factor of 10. Today, a 2.5-centimetre-wide drive found inside some portable music devices can hold 6 gigabytes – 6 billion bytes – of data. By 2010, Hitachi estimates that the same size device will be able to store 60 gigabytes, using perpendicular recording. Drive manufacturers have traditionally boosted the capacity of hard drives by packing sectors more closely together. But they are rapidly approaching the physical threshold of longitudinal recording, known as the superparamagnetic limit. Beyond around 15 gigabytes per square inch, it becomes difficult to maintain the distinct magnetic properties of each sector. Perpendicular recording promises to extend this limit by allowing sectors to be packed together more closely. As each sector is magnetised more deeply below the surface of the disc, each sector can have a smaller surface area and still retain its identity. Hitachi has so far used the method to achieve a density of just under 29 gigabytes per square inch. Perpendicular recording was first developed during the 1970s and several other hard drive makers, including Seagate and Toshiba, are currently developing similar technologies. “The health of this industry over the next 5 to 10 years is critically tied to the successful implementation and transition to perpendicular recording technology,” says Jim Porter, an industry analyst at US-based research firm Disc/Trend. Shu-ichi Iwasaki, of Japan’s Tohoku Institute of Technology, who helped develop perpendicular recording, also welcomed the progress. “I am very happy to see that the technology will come into use soon,
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