A good backup plan suggests that at least one copy of the backup should be stored off site for disaster protection. However, for the copies stored on site, such as incremental backups, a fire-resistant safe or vault can speed disaster recovery -- if it's the right kind of safe or vault.
Unlike a conventional safe, a fire-resistant safe is not especially burglar proof. However it will do a much better job of protecting your tapes and backup media in the event of a fire, which is a more common concern at most data centers.
But to be effective, a fire safe for backups needs to be designed for data-storage media, which are damaged at a lower temperature than paper documents. Fire safes are rated by Underwriters Laboratories as 350-degree and 125-degree safes, depending on the test they passed. Tapes and other data storage media need a 125-degree safe -- meaning the temperature inside the safe didn't get above 125 degrees Fahrenheit during UL's standard fire test.
Keep in mind that such safes are fire-resistant, not fire proof. There is no safe on the market that will resist every type of fire. The UL test simulates a standard structural fire where temperatures reach 800 degrees or so for a short time as the fire sweeps through the building followed by a number of hours of progressively lower temperatures as the fire debris cools down.
For more information on fire-resistant safes, see DataLink's FAQ.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.