THE cassette tape is about to make a comeback, in a big way. From the updates posted by Facebook's 1 billion users to the medical images shared by healthcare organisations worldwide and the rise of high-definition video streaming, the need for something to store huge tranches of data is greater than ever. And while hard drives have traditionally been the workhorse of large storage operations, a new wave of ultra-dense tape drives that pack in information at much higher densities, while using less energy, is set to replace them.
By Paul Marks
Researchers at Fuji Film in Japan and IBM in Zurich, Switzerland, have already built prototypes that can store 35 terabytes of data - or about 35 million books' worth of information - on a cartridge that measures just 10 centimetres by 10 cm by 2 cm. This is achieved using magnetic tape coated in particles of barium ferrite.
But the real debut for this technology is likely to be the Square Kilometre Array (SKA), the world's largest radio telescope, whose thousands of antennas will be strewn across the southern hemisphere (New Scientist, 2 June, p 4). Once it's up and running in 2024, the SKA is expected to pump out 1 petabyte (1 million gigabytes) of compressed data per day.
Current projections by the trade body Information Storage Industry Consortium show that although hard drives will be able to store 3 terabytes a piece in a decade's time, that still amounts to at least 120,000 drives a year.
That annual archive growth would swamp an experiment that is expected to last decades, says Evangelos Eleftheriou of IBM, who is part of a team working to build tapes for the SKA. By the time the telescope comes online, he and colleagues expect to be able to store 100 terabytes on a cartridge of a similar size to their prototype, by shrinking the width of the recording tracks and using more accurate systems for positioning the read-write heads used to access them.
Using tapes should cut down drastically on energy use, too. Data centres based on disc drive arrays use over 200 times more power than would a tape library of similar size, according to a 2010 study by The Clipper Group, a technology consultancy based in Rye, New Hampshire. That's because disc drives in large arrays tend to remain powered-up, so their platters spin continuously, in case data is required, says Jon Hiles of Spectra Logic, a digital archiving firm in Boulder, Colorado. But tape drives only use power when they are being read or recorded on, he says.
The downside of tapes is that they are slower to access than hard discs because they have to be fetched by a robotic mechanism, inserted in a reader and spooled to the right point. But the Linear Tape File System, which is being developed, expedites this process to make it comparable to disc drives, Eleftheriou says.
As storage needs skyrocket, hard drives won't be able to keep up and keep power down, Eleftheriou says. Density improvements in hard drives are facing physical limits that mean they can only add more power-munching platters. "It's time to take advantage of the low power and low cost of tape," he says.
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