This article can also be found in the Premium Editorial Download "Storage magazine: What to do when storage capacity keeps growing."
Download it now to read this article plus other related content.
WHILE THE OPTICAL storage industry is caught up in the Blu-ray vs. HD-DVD debate, it seems as if the battle lines are being drawn for what might turn out to be the next standards skirmish: holographic storage.
Work on the technology began more than 40 years ago and two companies--InPhase Technologies of Longmont, CO, and Japan's Optware Corp. with its Holographic Versatile Disc (HVD)--will finally ship the first commercial offerings late this year. InPhase's first Tapestry drive, the HDS-300R, will use 300GB write-once disks designed for professional archiving, complete with RFID identifiers. It has a SCSI interface, a 20MB/sec transfer rate, a MTBF of 100,000 hours and a rewritable design will follow. InPhase says the drive will scale to 1.6TB by 2009, and is planning other products like a 2GB postage stamp-sized device and 210GB on a credit card-sized unit.
Optware's first HVD product, the HVD Pro Series 1000, will store 200GB on a disk very similar--and, in fact, somewhat compatible--to DVD. By spacing the holographic cones at three micron intervals, the company has experimentally verified up to 3.9TB at a transfer rate of 1Gb/sec. Optware promises today's drives will be able to read tomorrow's disks, all the way up to the 3.9TB version. Optware has submitted HVD to the European Computer Manufacturers Association for standardization, and it will eventually go to the International Standards Organization.
But in the meantime,
The promise of holographic storage lies in its volumetric approach: Data isn't stored on the medium's surface; instead, it uses the third dimension by employing inverted cones approximately 500 microns thick at the top. Superimposed holograms share the same 3D space; the recording beam distinguishes them via different angles, phases or wavelengths. The theoretical limit is storing one bit in a cubic block the size of the light's wavelength. Practical densities will always remain much lower, but 10TB or more on a CD-sized disk is feasible. Holographic drives don't store bits, but pages of 60Kb or more, writing one page with a single laser flash. They can read and write in parallel: To achieve higher transfer rates, the orange-colored disk doesn't have to spin any faster.
Though not currently championed by any standards bodies, Optware's technology could greatly expand the reach of holographic storage by enabling things like combination holographic/DVD drives, physical on-disk encryption, or the use of holographic storage as an alternative to flash memory in consumer-device manufacturer items like cell phones and camcorders.
While other systems require separately angled signal and reference beams, Optware's beams are collimated (parallel) on the same axis, reducing the bulk and complexity of a read/write mechanism. This so-called collinear system can use pre-formatted disks with address "pits" that are similar to today's CD and DVD technology. While a blue-green laser reads and writes, a red laser ensures accurate positioning. Because the servo positioning is so similar to today's DVD, it's conceivable that future drives might be able to use both. Collinear technology is also capable of physical on-disk encryption, which holds great promise for digital rights management and other sensitive applications, says the company.
For now, the challenge is to get holographic storage into the hands of the enterprise. "With a little bit of luck, they'll make their ship date," says Dr. Hans Coufal, manager, science and technology at IBM's Almaden Research Center. Then the real issue becomes gaining "credibility for a new technology."
This was first published in June 2006