Misc

Tape backup vs. disk backup at customer sites

While the tape market is clearly declining and disk-based backup continues to pick up steam, many IT organizations are still fans of tape backup and have no plans to abandon it in favor of disk.

Tom Letourneau, network analyst for 500-employee Virginia Regional Medical Center in Virginia, Minn., for example, said his organization's disk-to-disk-to-tape backup strategy has served it well.

"I don't see us moving from tape for a long time to come," he said. "It's a technology that's been around long enough to have proven itself for storage. Hard drives have more environmental concerns than tape … [in terms of] energy use and just general storage. Not that this actually happens, but [if] someone sets a strong magnetic-force item next to a hard drive, they're more likely to lose data than tape is, at least that's my impression. The other issue is storage capacity. We can still fit a lot more data on one tape than we can on a hard drive."

Virginia Regional Medical Center has two tape libraries: a 48-slot LTO-3 library and a 40-slot LTO-4 tape drive. It backs up about 7 TB to 10 TB a week, first to a 12 TB SAN used just for backup, and then to tape.

Maurice Volaski, systems administrator for the Kennedy Research Center at the Albert Einstein College of Medicine, also has no plans to abandon tape in the near future. The 4,000-employee medical school has about 24 TB of data and has a two-drive LTO-4 tape library with 44 slots, with one of the drives being a recent purchase. "We're increasing our reliance on tape," said Volaski.

On the other end of the spectrum is a large credit union in the western United States with plans to almost completely eradicate tape from its data center in the next two or so years. The IT manager at the credit union, who spoke on the condition of anonymity, said performance and reliability problems have driven the financial institution from a D2D2T strategy toward a D2D backup strategy.

"It's not really meeting our needs," said the administrator. "We have [run into problems]. We have a lot of data to back up. We have a tough time getting everything backed up during our backup window. We could add more tape drives, but I'm not really sure that solves the problem long term. Tapes degrade, and we have fairly long retention periods for a lot of documentation because of financial industry regulation."

The credit union currently has four LTO-3 tape libraries, manages about 30 TB of data and backs up about 6 TB weekly.

National Semiconductor's corporate data center is also planning to lessen its reliance on tape, said Anthony Villegas, enterprise storage team lead. The company has already converted its mainframe's backup process to a VTL-based system. "We're going to be converting our distributed systems ... to virtual tape as well. We were very successful in the [mainframe VTL] implementation. Now that the economy seems to be picking up, we're able to expand our virtual tape and now convert our open systems from physical to virtual."

Villegas' group manages about 460 TB of data, with 20 to 25 TB backed up weekly. It currently has one LTO-2 tape library supporting its distributed systems, with 800+ slots.

Villegas said that the corporate data center will be almost completely tape-free within two years, though it will retain a few tape drives to be able to either create or read physical tapes if needed.

Disk ROI time frame?

The credit union administrator said she expects a disk-based backup system to cost about $150,000 to $175,000 and pay for itself in about two years. "Tapes are expensive. And we go through a lot of them," she said. "I'm buying thousands of dollars' worth of tape every year. And the amount of time it takes us to administer a tape system is astronomical. I have one person [who spends] at least 40% of his time … administering the backup system. If we don't have the tape administration, that really frees my resources up."

But Russ Fellows, managing partner of Evaluator Group, a storage-focused consultancy, cautions that it's unlikely that disk will be cheaper than tape over the long term. "It's all about what you include and what you exclude" in the ROI analysis, he said. "It can be possible to say that disk is less if you use a very high cost for personnel expense and assume that tape takes a lot of time and that disk takes no time. Both assumptions are wrong."

Fellows said his research on the topic shows that disk is generally 2x to 10x more expensive than tape. He said that oftentimes, customers forget to account for a secondary disk system for disaster recovery purposes, when moving from tape to disk-based backup, as well as network costs to the DR site, and power and cooling costs for the disk. "Even with data deduplication, I've never seen a realistic TCO that had disk being less than tape. In some extreme cases, it can be equal."

Sanjiv Purba, partner at 50-employee systems integrator Infomaxium in Toronto, which has mostly enterprise-level clients, said that while there's momentum toward disk among his customers, he's not finding a huge preference for disk or tape. In general, he said, it all boils down to cost.

"Tape is still very good for volume offsite. But if we can prove that the total cost of ownership for disk can compare, then they're open to that." Purba said that customers want a quick ROI but if they can see an ROI within three or four years, they're comfortable making the switch.

The encryption question

With LTO-4's native support for encryption, are customers actually encrypting more of their tape data? It seems that the native support in LT0-4 isn't enough to push people toward encryption if they weren't already doing it. Infomaxium's Purba said he hasn't seen a lot of tape encryption among his customers.

Virginia Regional Medical Center encrypts all data on tape natively on its LTO-4 library, and also performs encryption via backup software on its LTO-3 library. "We get a performance hit doing it through software rather than doing it on hardware, but it's not enough of a hit to not do it," said Letourneau. "I'd rather take the extra time and encrypt the data than have the very, very slight risk of losing a tape."

The credit union in the western United States also encrypts its tape backup data.

Albert Einstein College of Medicine's Volaski has a different view on encryption: "To me, encryption on tape is dumb. It's gross overprotection," he said. "Think about a laptop and a tape and [say] both of them get stolen. It's going to be much easier for a thief to get data off of a laptop than a tape. If a thief gets ahold of an LTO-4 tape, what's he going to do with it? You've got to have an LT0-4 drive, and even if he has that, how's he going to [have the right] program? And even if he had the program, it's still password-protected."

Beyond the issue of established beliefs about the usefulness of tape encryption, the difference in opinions between Letourneau and Volaski may be explained by the type of data they're protecting. Virginia Regional Medical Center is obviously protecting patient data, whereas Albert Einstein College of Medicine is not. "We're mostly academic research here, so it's mostly academic data," said Volaski. "Most labs are doing work on animals or on cells" so there's not the same kinds of concerns as a financial or health care company.

National Semiconductor's Villegas takes a minimalist approach to encryption for tape backup: "Our backup software implies that it has some sort of encryption, so it's a very low level of encryption, a first level of defense."

This was first published in September 2009

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