by David Shayer

Some things are inevitable. Death, taxes, and disk crashes. One day you will try to open an important file, only to receive a dire error message. Or perhaps you'll discover that an entire folder has vanished. Worse yet, maybe your Mac won't even boot, thanks to some sort of disk corruption.

Fortunately, you have a full backup of all your data, so you just restore the missing data from your backup, and you're back in business. What's that you say? The last time you backed up was during the Reagan administration?

If an ounce of prevention is worth a pound of cure, then surely the most effective disk repair program is actually a reliable backup utility. My favorite is Dantz's Retrospect. But whatever backup program you choose, you must use it regularly, so you have a current backup when your hard disk is called to that great clean room in the sky. (See the TidBITS article series, "Have You Backed Up Today?" for more details on setting up a good backup strategy.)

Yet just as so many of us would prefer to lose weight by taking a magic pill rather than through diet and exercise, we'd rather fix a corrupted disk with a disk utility, rather than restoring from a backup, even when a recent backup is available. It can take many hours to do a full restore from a backup, whereas a good disk utility can often fix minor disk errors in minutes.

Some of the Macintosh world's favorite disk repair programs have recent upgrades, and here I'll compare the Norton Disk Doctor tool in Symantec's Norton Utilities 8.0 ($100), Alsoft's DiskWarrior 3.0 ($80), Micromat's Drive 10 1.1.4 ($70), SubRosaSoft's DiskGuardian 2.2 ($70), and Apple's Disk Utility (free). Although these programs contain a wide variety of disparate features, I concentrate on their disk repair functions in Mac OS X. I chose not to include Prosoft Engineering's Data Rescue X, because it recovers files onto another disk and does not repair the damaged disk itself.

The user interface and ancillary features of a disk repair program are secondary, because in the event of disaster you care about only one thing: will it get my data back? So let's concentrate on the heart of the issue: what are the most common disk errors you may experience, and which disk repair programs can save your bacon when you're unfortunate enough to suffer disk corruption?

In my experience, most people run into three general categories of disk problems: hardware failure, bad sectors, and damaged directories. After a brief examination of how you get started with these programs, given that you can't repair an active startup disk in Mac OS X, I look at the worst type of problem - hardware failures, after which I examine the soft errors and compare the performance of the disk repair programs.

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