Every Mac volume has a catalogue – a kind of table of contents – that the OS uses to find your files. If it becomes badly damaged and you don’t have a backup, your data could be lost. Alsoft’s DiskWarrior comes to the rescue by repairing mangled catalogues, displaying impressive stability and reliability for a 1.0 release. DiskWarrior’s sole focus is the reconstruction of catalogues, a process that’s beneficial for healthy as well as broken catalogues. Unlike Symantec’s Norton Disk Doctor, DiskWarrior doesn’t examine your disk, run through a checklist of possible errors, and fix them one by one. Instead, DiskWarrior takes a holistic approach: it looks at the existing catalogue data, collects additional information the OS has stored elsewhere on the disk, and uses all the information to re-create an entirely new catalogue. By rebuilding a damaged catalogue, DiskWarrior can resurrect previously deleted files as well as those believed to be lost. If the catalogue is healthy to begin with, rebuilding has a measurable speed benefit because a fresh catalogue is much easier to search. On a test volume, the Mac OS’s Disk First Aid took 1 minute and 44 seconds to scan the catalogue; after rebuilding, it took only 39 seconds. (To rebuild a disk’s catalogue without DiskWarrior, you’d have to back up, initialize, and restore the disk; simply defragmenting files with a disk optimizer doesn’t have the same effect.) And DiskWarrior proved remarkably reliable: not once during testing did the program create a bad catalogue or cause any disk-related vexations. DiskWarrior’s user interface is remarkably straightforward. You simply select a disk and press the Rebuild button and DiskWarrior builds a new catalogue. Once it’s finished rebuilding, you can preview how your disk will look with the new catalogue: DiskWarrior mounts both the original and rebuilt catalogues as read-only disks and lets you explore them in the Finder. You can then use the preview catalogue to copy files off the disk, without changing anything on the disk itself. If you decide you want to keep the rebuilt catalogue, DiskWarrior uses it to replace the old one. Only one noticeable flaw appeared during testing: if a disk was damaged in such a way that the Mac OS refused to mount it, DiskWarrior wouldn’t work with it.


Although it’s not as comprehensive as Norton Disk Doctor, DiskWarrior performs its one crucial function well and should be part of any collection of disk tools. Not only is the program useful for sprucing up healthy disks but it also increases your odds of recovering files that might otherwise be lost.

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