Storage in 3D

British journalists use the affectionate term “”boffin”” to describe the scientifically inclined, much the way we call the technologically enthusiastic “”geeks.”” Glenn Horner’s got a labful of boffins.

Horner is a co-founder of Aprilis Inc., a Polaroid spin-off developing new optical technology

that could cram more data than ever onto a humble disk. At a 30,000-square-foot lab in Maynard, Mass., a staff of about 30 — mostly researchers — are shedding some light on holographic storage.

While a CD or DVD stores data as a stream of ones and zeroes on the surface of a disk, holographic storage systems would write a three-dimensional image through the entire depth of the medium. Theoretically, a CD-sized holographic disk could hold up to 1TB of data.

Writing to a holographic disk takes two laser beams. The first, called the object beam, projects the digitally encoded data. The second, the reference beam, turns that data into a 3-D image. “”You’re writing holograms,”” says Horner — a visual representation of the data, pages of information rather than single bits.

When the disk is read with the reference beam, the data beam is reconstructed — thus, the data is retrieved. But if it’s read with an object beam containing data, the reference beam is reconstructed. The intensity of the reference beam is a reflection of how closely the data being read matches the data in the object beam. This leads to deliriously fast coarse searching of mounds of data, according to Horner.

Researchers began writing through media 200 microns thick, but most of the work being done now is on 400-micron media. While theoretically, there no cap on the thickness of the medium, “”There are limits to how deep you can practically go,”” says Horner — probably in the several-millimetres range. “”You don’t want to go too thick, too fast.””

Holographic storage’s characteristics position it as an archival technology. There’s the quantity of data that can be stored in a convenient form factor. There’s the archival permanence — “”You couldn’t erase it if you wanted to,”” Horner notes. The speed with which massive volumes of data can be searched and a transfer rate on the order of 100MB per second also make it an archival natural, especially for space hungry applications like broadcast, medical and satellite imagery, he says.

(Is it ironic that images are converted into a stream of data, which is then converted to a holographic image to be stored? Discuss).

Holographic storage would likely take the form of a near-line system, much like a tape jukebox, according to Horner.

O.K., Star Trek fans, here’s your assignment: We’re all familiar with the Holodeck from Star Trek: The Next Generation (Well, you are, anyway — I never watched anything past the original series. I couldn’t watch a spaceship being run without Mr. Scott there to lend some sanity to the proceedings — ye cannae change the laws of physics, y’know. What was I on about? Oh, right). If a CD-sized holographic disk could store 1TB of data, how much data could be stored by the TNG holodeck? For the sake of argument, let’s assume the holodeck is the size of a squash court — and I have no idea how big that is, as my physical conditioning will attest. Show all your work. For bonus points, give an analogy — for example, a stack of textbooks that would reach from here to the edge of the Romulan empire, or at least France.

And watch for our IT Business Rport on storage, shipping with your print subscription in early April. Don’t have a print subscription? The link’s on this page.

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Dave Webb’s editors took great pains to ensure this column is hologrammatically correct.

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Dave Webb
Dave Webb
Dave Webb is a technology journalist with more than 15 years' experience. He has edited numerous technology publications including Network World Canada, ComputerWorld Canada, Computing Canada and eBusiness Journal. He now runs content development shop Dweeb Media.

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