Many backup-minded users prefer to store their backups on ordinary external USB drives, but I prefer a removable-cartridge system. It lets me use a single drive unit that stays attached to my system, while I cycle through a stack of removable cartridges so I always have a full backup on-site and two or more other backups stored safely somewhere else. For years I've used Iomega REV drives such as the Iomega REV 120GB USB, but the Tandberg Data RDX QuikStor system ($555 street, with one 320GB cartridge) offers almost twice the speed of the Iomega REV 120GB and more than twice its storage capacity on Tandberg Data's 320GB cartridges—with 500GB cartridges just announced. (The Tandberg Data drive is also sold under license by Hewlett-Packard as the HP StorageWorks RDX320.

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The one fly in Tandberg Data's ointment—and it's a big one—is the high price of its cartridges: typically $385 (street) for a 320GB cartridge, and $480 for the new 500GB cartridge. (By contrast, you can get a five-pack of Iomega REV 120GB cartridges for less than $300, or even a 300GB external USB drive for about $80.) Since you can now buy a 500GB external hard drive for about a hundred bucks, you could buy five external hard drives for roughly the same price as the QuikStor with a single 320GB cartridge. If, on the other hand, you've got the budget for it, you might consider the Tandberg Data unit for the extreme ruggedness of its cartridges, which are designed to survive the kind of rough treatment that might demolish many standard USB drives. I don't have the kind of lab that can test cartridges for ruggedness, but I deliberately dropped the Tandberg Data cartridge 6 feet to a ceramic-tiled floor—twice. The cartridge wasn't damaged in the least, and passed all of its diagnostic tests.

The compact case, with thick rubber bumpers on the long edges, measured 2.2 by 4.4 by 7.0 inches (HWD). Each cartridge measures 1.0 by 3.5 by 4.7 inches (HWD)—small enough to fit in some shirt pockets. The cartridge has a plastic write-protect switch at the back and connects to the drive internally through a standard SATA data and power connector. (Purely as an experiment, I tried connecting the cartridge directly to a set of SATA power cables to see if I could use the cartridge without the drive enclosure, but the computer didn't recognize the cartridge. Needless to say, Tandberg Data never even suggested that the cartridge was designed to be used without the drive unit.)

The external USB model that I tested is ideal if you plan to back up multiple machines and wish to plug the drive in to whichever machine you need to back up. But a power-hungry USB drive like this one requires a separate power supply and a tangle of wires. So, if you're backing up a single machine, or a group of networked machines, you might want to consider the internal SATA version of this drive, which will probably be an even faster performer because SATA connections are faster than USB ones.

For software testing, I used the RDX drive with our Editors' Choice drive-imaging product, ShadowProtect Desktop, and also with the RDX FileKeeper backup software that ships with the drive. ShadowProtect Desktop was able to back up a 22GB partition to the RDX drive in only 11 minutes 54 seconds—almost twice as fast the Iomega REV120. The RDX ships with its own backup software, called RDX FileKeeper, a custom version of Yosemite FileKeeper from Yosemite Technologies. Because RDX FileKeeper operates continuously in the background, backing up every file on your disk and also making multiple-version backups of data files, it inevitably takes more time to back up your disk than a standard backup program like ShadowProtect Desktop, which creates a backup as quickly as possible and then quits. In my real-world testing, RDX FileKeeper required 51 minutes 10 seconds to back up my entire disk while I continued to work in Microsoft Word in the foreground. But you shouldn't conclude that RDX FileKeeper is therefore a worse program than the much faster ShadowProtect Desktop, because the two programs serve different functions and work in different ways. FileKeeper runs continuously in the background and automatically makes backups of multiple versions of your files, and ShadowProtect Desktop takes periodic snapshots of your disk and backs up only the versions of your files that were current when it took the snapshot.

You can recover these earlier versions by right-clicking on the current version of the data file in Windows Explorer and choosing the restore option. This is similar to the Restore Previous Versions feature in high-end versions of Vista, but better than Vista's backup because the earlier versions are stored on the cartridge, giving them a better chance of surviving disk disasters. The RDX FileKeeper software also makes the backup cartridge bootable so that, in case of disaster, you can boot directly to the cartridge and run its disaster recovery program to restore your disk—or the program can create a bootable CD that performs the same emergency restore function by restoring your system from a backup stored on a cartridge.

A further option in RDX FileKeeper simply makes a complete copy of your entire system for storage off-site. RDX FileKeeper is ideal for anyone who doesn't want to think twice about making backups and who wants the convenience of right-click restores of earlier versions. I still prefer ShadowProtect Desktop for my backups because of its blazing speed and because it makes loading a backed-up disk into Windows as easy as if it were a read-only hard disk, but RDX FileKeeper is ahead of the crowd in terms of allowing easy previous-version restores.

I like Tandberg Data's RDX QuikStor for its high-capacity cartridges and for its ruggedness and flexibility. I don't like its pricing. In the current economic climate, you probably don't have money to burn, but backup is a necessity, not a luxury, and there's no denying that in the world of backup, the Tandberg Data RDX is a star performer. In its category of cartridge drives, it's the best, but its price means that we have to recommend standalone USB drives as a far cheaper alternative.

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