Music lovers may have long forsaken them, but magnetic tapes still reign supreme when it comes to storing vast amounts of digital data. And new research from IBM and Fujifilm could ensure that tape remains the mass storage medium of choice for years to come for at least a decade.
At IBM's Zurich Research Laboratories in Switzerland, researchers have developed a new tape material and a novel tape-reading technology. In combination, they can store 29.5 billion bits per square inch, which translates to a cartridge capable of holding around 35 terabytes of data--more than 40 times the capacity of cartridges currently available, and several times more than a hard disk of comparable size.
The researchers used a relatively new magnetic medium, called barium ferrite. In cooperation with researchers from Fujifilm's labs in Japan, they orientated the barium ferrite magnetic particles so that their magnetic fields protrude perpendicularly from the tape, instead of lengthways. This means that more bits can be crammed into a given area, and the magnetic fields are stronger. Furthermore, these particles allow thinner tape to be used, meaning12 percent more tape can be stored on a single spooled cartridge.
Increasing the density of data that can be stored on a tape makes it more difficult to reliably read information. This is already a problem because of electromagnetic interference and because the heads themselves will retain a certain amount of residual magnetism from readings. To overcome this, the IBM group developed new signal processing algorithms that simultaneously process data and predict the effect that electromagnetic noise will have on subsequent readings.
Hard disks can store more data on a given surface area than magnetic tape, and the data on a disk can be read faster. But because hundreds of meters of tape can be spooled on a single cartridge, the overall volumetric data density of tape is higher, says Evangelos Eleftheriou, head of the Storage Technologies group at IBM Zurich.
Crucially, tape storage is also much cheaper. "What's most important is the cost per gigabyte," says Eleftheriou. Solid state drives cost between $3 and $20 per gigabyte. In contrast, it costs less than a cent per gigabyte to store information on magnetic tape. In the third quarter of 2009, the global tape market was worth more than half a billion dollars.
Extending the life of magnetic tape technology could delay the arrival of new storage technologies, particularly holographic storage. Experimental holographic discs, which use patterns of light interference to hold multiple pieces of data at a single point, can already hold several hundred gigabytes of data. The technology is expected to eventually allow terabytes of data to be held on a disc.
"Tape still wins, but only at very high data volumes," says James Hamilton, a vice president and distinguished engineer on Amazon's Web services team, in Bellevue, WA. Tape is most suitable for "cold storage"--when data is not accessed frequently. But the volume of digital data that needs to be stored is increasing rapidly, so Hamilton says there's a real need to try to squeeze more out of tape.
It could take another five years before the new tape technology is ready for the market, Eleftheriou admits. "But we have shown that there is still at least another 10 years of life in it," he says.
By Duncan Graham-Rowe
From Technology Review