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Once you've come up with a schedule for making backups, you need to figure out where to store the backup media. In one of the saddest events we've seen, a network administrator simply left a tape in the drive and told his backup system to make a full backup of the server daily, because his tape drive held more data than his server. After several uneventful months, a burglar stole the server, with its internal tape drive and, of course, all the company's data. A safe is a better solution.

Where you store your backups has a significant impact on the time and effort involved in restoring data and on the effect of small disasters, such as burglaries and fires. Keeping your backups online in a tape changer or library makes it easy to restore the important file that someone accidentally deleted, but this leaves your backups vulnerable to larger disasters, such as fires and floods in your data center. The traditional solution to these problems is to store a separate set of backups off-site.

This brings about the question of how to manage your off-site backups. For small businesses, off-site backups often mean a safe-deposit box at the local bank, a safe at the owner's home or even the trunk of the IT director's car. While inexpensive, these solutions are less than perfect. If your building catches fire on a Friday afternoon, you may not be able to get into the safe-deposit box until the bank opens at 9 a.m. Monday. If your backups are in your car, they aren't really off-site when you're parked at work, are they?

Large data centers should arrange contracts with records-storage companies, such as Comdisco or Iron Mountain Co.'s Arcus Data Security, to pick up storage boxes weekly or monthly and deliver them back on demand. All you need to do is keep a log of what data is on what tape in which storage box and pay the company a few hundred dollars a month for pickup and delivery. Remote plants and offices might find that overnighting the backups to headquarters so the central IS staff can manage them is the most cost-effective solution.

Another option for off-site backups is electronic vaulting. Vendors ranging from SkyDesk and Xdrive Technologies to disaster-recovery powerhouses Comdisco and SunGard let you ship your data to a remote data vault across a WAN or the Internet. You'll probably find that the fees and bandwidth requirements for remote vaulting are not cost-effective for full backups. On the other hand, the cost and time required to save a small to midsize company's critical files at a remote data vault can be less than $25 per month for a few hundred megabytes.

It's also a lot easier to keep electronic off-site backups up to date. We've even had a client use these services to recover data from a salesman's lost laptop. That client used a remote vault to store the Microsoft PowerPoint presentations and other files salespeople in the field need. Rather than miss an important presentation, the salesman just bought a new laptop and used the high-speed Internet access at his hotel to recover.

How Long is Too Long?

The last major question is how long to keep the backup media. From a purely technical point of view, it's easy to say forever. Unfortunately, forever has a few drawbacks. The first is cost. With media for tape technologies like DLT (Digital Linear Tape) and LTO (Linear Tape Open) running more than $100 each, an infinite storage policy can cost you a few extra bucks. More significant is the legal liability. Should your company ever be the target of a lawsuit, the plaintiff could subpoena all files related to the suit. You would then have to restore all your stored backups to search for related files and e-mail messages that were thought to have been deleted by their creators. Finally, data on recordable media has a finite lifetime. Tapes and CD-ROMs can be counted on to hold their contents only for five years or so.

While it's outside the scope of this article to go into detail about the various tape technologies, we do want to remind you that media formats may have a shorter lifetime than the data that's stored on them. For example, NASA's Jet Propulsion Laboratory is facing a crisis due to the huge libraries of data from space probes like Pioneer that are stored on aging seven-track tapes for which readers are no longer made. When you decide to change tape formats -- from QIC (quarter-inch cartridge) to DAT (digital audio tape) or DLT to LTO -- make sure you retain a tape drive to read those old backups. Even better, take the opportunity to review your old backup libraries, discard the data that you no longer need to or should retain, and transfer the important data to new media.

In short, while there is no one perfect backup strategy for every organization, the path to an effective strategy is to determine what must be protected, for how long it will be feasible to restore and how long it should be retained. The answers to these questions will lead you to an effective backup strategy.