Gillian Blease

THE digital age has turned people and companies into data hoarders. Home computers bulge with music tracks, photographs, videos and e-mails; and government regulations and industry trends mean that companies, financial institutions and medical organisations are piling up information on an unprecedented scale. For really large amounts of data, storage capacity is no longer measured in gigabytes, terabytes or petabytes, but rather by the size of the warehouses needed for the discs, cartridges or tapes that carry them.

But a new storage technology, which will go on sale in the next few weeks after years of development, can squeeze more onto a small disc or cartridge than ever before. With the potential to store hundreds of times more data on a disc than today's DVDs or even the latest high-capacity Blu-ray and HD-DVD discs, holographic storage is about to hit the market.

Unlike DVDs, which store data in thin layers just beneath the surface of the disc, holographic storage encodes information in three dimensions, within the volume of the disc. This will enable the first holographic discs to store a colossal 300 gigabytes of data—12 times more than the latest Blu-ray discs and 60 times more than a standard DVD. And within a few years this capacity is expected to increase more than fivefold to 1.6 terabytes (1,600 gigabytes) of data—enough to store five seasons of a television drama, in high-definition video, on one disc. But as is so often the case with new storage formats, rival standards are under development.

That said, the various technologies work on the same basic holographic principle, pioneered in 1963 by Pieter van Heerden of Polaroid Research Labs in Cambridge, Massachusetts. Digital information is stored in a holographic material in much the same way that pictures are stored in traditional holograms. And just as holographic images are able to show slightly different perspectives of an object or scene, taken from slightly different viewpoints, holographic data-storage systems can store multiple “pages” of digital data at different angles in the material.

Each page consists of a pattern of 1m or so black and white squares in a grid-like pattern, representing the zeroes and ones of digital information. This pattern is displayed on a small flat-panel display, which is illuminated by a laser beam so that the pattern is encoded onto the beam. This “signal beam” then meets a separate reference beam, and where the two beams intersect they create an interference pattern in a light-sensitive medium. A chemical reaction occurs so that the interference pattern, or hologram, is permanently recorded into the medium.

The signal beam can be recreated by illuminating the medium with a beam identical to the original reference beam. The resulting pattern is projected onto a detector and the entire page of 1m bits can be read out at once. Crucially, hundreds of such patterns, and hence hundreds of pages of data, can be superimposed within a given volume of holographic material, provided each is recorded at a slightly different angle (see diagram). Hence the massive storage capacity.

End of the reel for tape?

All this could be good news for companies maintaining mountains of data, says Mukul Krishna, an analyst at Frost & Sullivan who specialises in digital media. “With the same footprint, they will literally be able to triple or quadruple their ability to store data,” he says. At the moment the mass-storage medium of choice is magnetic tape, which has the advantage of being cheap. But magnetic tapes must be carefully stored and managed, which can include periodically copying important information from old tapes onto new ones to ensure that it can still be read. And as the volume of data being stored continues to increase, the cost of maintaining tape archives is growing fast, says Mr Krishna. The average installed storage capacity of a Fortune 1000 company grew from 198 terabytes in early 2005 to 680 terabytes in October 2006, according to figures from Deloitte, a consultancy.

In particular, corporate-governance regulations in many parts of the world require companies to archive electronic records for many years for compliance purposes. “E-mail archiving alone is one of the largest applications and expenses facing many IT departments,” says Liz Murphy of InPhase Technologies, a spin-out from Bell Labs based in Longmont, Colorado, which will be the first company to launch a holographic disc-drive this summer. Another big trend, she says, is the growth in storage of financial records, scientific data, medical images and other records that do not necessarily need to be archived, but may need to be called up quickly. This is possible using libraries in which special robots load cassettes into tape drives when required, but a holographic disc would be much quicker.

The emergence of high-definition video formats could also provide a new market for the technology, as television-production companies and broadcasters grapple with a sudden and dramatic increase in their storage requirements. InPhase is testing its first holographic disc-drive, called the Tapestry 900, in conjunction with partners such as Ikegami Tsushinki, a Japanese firm which makes video cameras for the television industry. The new technology allows Ikegami to dump all unedited footage from its cameras onto holographic discs.

 Gillian Blease

As well as being holographic, the Tapestry 900 drive works differently from traditional disc-based systems. Rather than spinning continuously like a DVD or CD, its cartridge-based discs remain stationary as pages of data are written onto a given section of the disc from 350 different angles. The disc is then rotated very slightly so that the next batch of pages can be written. This might sound slow compared with rival technologies, but it is in fact very fast because the page-based approach means that rather than being written and read bit by bit, information is transferred in batches of around a million bits at a time, says Lisa Dhar of InPhase. Accordingly, InPhase's system can read and write at a rate of 160 megabits per second.

Although it is initially aiming at the corporate market, InPhase hopes its technology will eventually be available in consumer products, too. As well as offering much higher capacities than today's high-definition disc formats (Blu-ray and HD-DVD), holographic discs ought to be more difficult to counterfeit, which should appeal to the film industry. InPhase is developing the replication technology needed for the mass distribution of films, games and software. It is also working on ways to make its holographic discs re-writable. At the moment they are a “write once, read many times” (WORM) technology, like CD-R and DVD-R; once written, data cannot be deleted or changed.

But in consumer markets InPhase could face competition. DCE Aprilis, a company spun out of Polaroid in 1999 and then acquired by Dow Corning, is licensing its holographic-storage technology to several big consumer-electronics firms. And a start-up called Optware has devised its own holographic-disc format, called HVD, which is of course completely incompatible with InPhase's system. Products based on these rival technologies are still some way off, but their backers claim that they are technically superior to InPhase's approach. Both DCE Aprilis and Optware claim to have achieved a data-transfer rate of one gigabit per second, which makes InPhase's technology seem slow—though it is expected to reach higher speeds in future.

Just an illusion?

Mr Krishna maintains, however, that the “killer application” for the technology is nevertheless in mass storage for the corporate market. Quite apart from the fact that it takes years for consumer-electronics companies to agree and adopt new standards, there is simply more money to be made from selling to businesses, he says. Tellingly, as well as pushing the HVD format, Optware is also developing a holographic-storage system for corporate use that stores information on rectangular cards rather than discs.

But despite plans to launch products in early 2006, Optware has yet to produce anything. And some observers remain doubtful that holographic storage will be commercially viable any time soon. IBM, once a leader in the field, has decided to concentrate on improving existing magnetic-tape systems instead, says Matthias Kaiserswerth, director of IBM's Zurich Research Laboratory in Switzerland. InPhase's first drive will cost $18,000, and each 300-gigabyte cartridge will cost a further $180. Holographic-storage technology certainly works and has all kinds of potential uses. But until the prices come down, demand for this unusual new technology could be all too holographic in nature: apparently there, but upon closer inspection proving to be only a mirage.