Deep Storage: Does Tape Have a Place?

You can set your watch by IT. Every couple of months, a pundit announces that with the falling price of SATA disks and copious network bandwidth, we should put tape on the pile of obsolete technology with core memory and drum storage. I have my own love-hate--OK, mostly hate--relationship with tape; I wouldn't shed a tear if I never dealt with tapes again. But is the tapeless data center reasonable for a typical midsize company, or is it as likely as the paperless bathroom?

I've come to the conclusion that small businesses are better off without tape. Online data vaulting is perfect for small businesses. Sign up for service from U.S. Data Trust, eVault, LiveVault or any of a multitude of vendors and you'll get backup software and the disaster protection of off-site storage that you never got with tape--all for as little as $100 per month for 10 GB. That's enough for the QuickBooks files and other critical small-enterprise data.

Sensible folks realize that encryption, and the vaulting vendor's need to stay in business, make storing data on someone else's servers safe. They worry, however, about how a total server failure and a total restore of their 10 GB would take 33 hours over a low-end DSL line. Sure, a restore from tape would go much faster, but not all data carries the same priority in such a restore. Since a QuickBooks file is typically 500 MB, you could restore it to a workstation while rebuilding the server. Accounting is up and running before you even have backup Exec reinstalled.

Larger businesses, with more data to protect and a staff that's capable of managing backups, aren't going to find an online vaulting service nearly as attractive. They'll have to pay bigger storage fees and increase their Internet bandwidth to get reasonable restore times. That means backing up on-site.

Performing backups on-site, however, doesn't necessarily imply tape. Snapshots, or disk-to-disk backups, allow for on-demand single file or other small restores more easily than restoring from tape. But disk space must match the service level. A promise to be able to restore files back 30 days implies having enough disk space for 30 days of incremental backups. If a server dies or a volume is corrupted, restoring from disk is similarly easier and faster than from tape.Disasters happen, though, and you'd better have data stored off-site. Sending tapes off-site is the least expensive protection against a catastrophe, but it means at best a one-to-two-day recovery target. Going tapeless means replicating data to a disaster-recovery site, collocation facility or vaulting provider. Although it's cost-effective for most critical applications, sending tapes off-site weekly may be good enough, and a lot less costly, for others.

Using these strategies, midsize companies can live without tape backup; archiving, however, is another matter. Except for a tightly regulated industry like financial services, archival storage often means keeping an occasional full backup on the shelf, or at a records-storage facility, for several years. Keeping such long-term data on disk means totally rearchitecting the archival storage procedure, or having 20 to 30 times as much disk space in the archive arrays as in your production arrays. While possible, it comes with its own power and cooling challenges.

One seldom-considered advantage for tape is that tapes on the shelf are immune to software-inflicted damage. If backups are exclusively on a disk array, and the backup server--driven by a virus or other computer psychosis--deletes or corrupts the file system on the array, all your backups are gone. Daily backups to the disk pool, along with the occasional copy to tape, should let you sleep better.

The bottom line: Hang on to your existing tape libraries and use them for archival and offline copies. Tape shouldn't be the first line of defense, but it makes an excellent fall-back defense--one you shouldn't be without.

Howard Marks is founder and chief scientist at Networks Are Our Lives, a network design and consulting firm in Hoboken, N.J. Write to him at [email protected]. 6607