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Users debate best media for archiving

Optical disk is the most reliable, but disk-to-tape is more frequently used for backup and archiving. Users weigh the pros and cons of each.

When doing archiving in-house, companies have two tried and tested options for storing data for the long haul: tape and optical disk. The reasons for picking one versus the other are black and white, according to users.

One company that has gone the optical route for archiving is Chittenden Corporation, a bank holding company headquartered in Burlington, Vt. Chittenden is using a G-Series UDO (ultra density optical) Library from Plasmon Plc. to store financial images and reports. Chittenden keeps one copy of its optical disks on site and then sends another off site.

Steven Jones, applications support manager at Chittenden, said the company chose the Plasmon library because of its expandability. The library ranges from six to 12 UDO drives and can contain up to 164 cartridges. Chittenden's previous optical system, an HP SureStore magneto optical library, only had two drives.

Jones said that in banking, most data has to be retained for seven years because of government regulations. Mortgage data has to be held for the life of the loan, which can be 30 years. "Optical is permanent media. I'm in a regulated industry, so stability and reliability is the most important thing," he said. "Tape is good for backup, but not long-term archiving. It doesn't age well: it stretches, and formats are always changing."

Bob Mason, director of publishing systems at The Dallas Morning News, agrees that permanence and reliability of data is king and doesn't believe tape can deliver on this promise over the long haul.

Mason, another user of Plasmon's G-Series UDO Library, said that the newspaper faces Sarbanes-Oxley regulations, as well as internal regulations requiring the paper to maintain permanent records of all published information.

"Tape does not prove the guaranteed reliability that optical can provide ... Data is an asset and must be protected with the guarantee that it will be available generations down the road," he said.

Tape's advantages

Peter Gerr, analyst at Enterprise Strategy Group (ESG), Milford, Mass., points out that for sheer capacity and price, tape is hard to beat for archiving. "The latest LTO tape has 800 GB compressed per tape. UDO, though light years ahead of previous optical versions, still only has 30 GB per platter."

Jeff Caldwell, director of storage and planning at the Chicago Board Options Exchange (CBOE), uses a disk-to-disk-to-tape approach, keeping data on StorageTek Corp. D178 and D280 disk subsystems, and then moves it to a StorageTek 9740 tape library.

Caldwell hasn't ruled out using optical disk for archiving, but for now, points to its high price compared to ATA disk and its lack of capacity compared to tape as reasons CBOE has stayed off optical. "Also, we tend to change vendors from time to time and it's cheaper to migrate and recycle disks," he said.

Similarly, Harvard Medical School and its six affiliated hospitals adheres to a tiered storage architecture, with 100 TB of medical and financial records and images stored on EMC Symmetrix DMX, Clariion and Centera, and then backed up by StorageTek Powderhorn tape libraries.

John Halamka, CIO Harvard Medical School, passed on optical because "transfer time to and from optical is much slower than both tape and disk." Large documents such as images and video -- common in the medical field -- can compound the problem. "The size of the documents makes retrieval 10 to 20 times slower with optical," Halamka said.

Like Caldwell, Halamka agrees that switching vendors or technologies is also more difficult with optical. "Just because optical storage lasts a very long time does not mean the equipment to read and write optical lasts anywhere near as long."

ESG's Gerr sums up that "tools to manage optical have not evolved like disk and tape management tools." And despite optical's long-term reliability, he said it's not practical cost-wise for large enterprises to archive only to optical. "Maybe for smaller companies it works, but I've yet to see a TCO model that can justify archiving enterprise levels of data to optical. Cheap disk right now costs between $2,000 and $10,000 per terabyte, and I can't see optical matching that."

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