Mac Disk Repair Utilities

by norith on January 4, 2009

in Uncategorized

A friend’s Mac needed some hand holding the other day and I pulled out all of the repair tools that I’ve collected over the years. The best one of all is another Mac itself because you can put the sick Mac into target disk mode (hold down the ‘T’ key while it’s booting) and you’ll see it’s disks as FireWire attached disks on the repair Mac. Of course this assumes that both Macs support Firewire — Apple is changing its mind here with the latest MacBooks.

From the repair Mac you can now run disk utilities against the sick drive without the interminable wait of booting from a CD or DVD disk. And you can also copy over any important files assuming you can get to them (and that for some weird reason they’re not in your Time Machine backup — you are using it aren’t you?).

One of the really neat target disk tricks is to put the repair computer into target disk mode and use it’s DVD drive to boot from a Mac OS disk or repair disk if the sick Mac’s DVD drive is bad. This is also handy if the sick Mac has only a CD capable drive and you need to boot from a DVD disk. The normal Mac boot key trick of holding down the ‘C’ key to boot from CD won’t work in this case though, use the boot disk chooser interface instead by holding down the ‘Opt’ key while the Mac is booting. A menu of all attached system disks will appear allowing you to choose a Firewire attached DVD drive and proceed (by clicking on the right arrow button in the screen.)

So then we come to volume repair utilities themselves. What’s the best option? I’ve had mixed results with TechTool Pro though it has many handy diagnostic features and sometimes will save the day. Diskwarrior is my fave as it doesn’t attempt to simply correct the damaged file system tables but instead replace them with a rebuilt one. It walks the file system and builds a new table structure from scratch. Apple’s own Disk Utility is sort of a ‘first try’ tool. I dont’ expect it to fix the problem but it’s aways a good choice to start with.

Fixing disks is something that you don’t want to be doing and you don’t pay attention to until you need to. My collection of tools had grown old with outdated boot disks and warning screens about not being tested with this version of the OS.  Updating them is frustration itself. Neither Diskwarrior or TechTool Pro boot disk updates can be downloaded, you have to pay for a physical disk to be shipped to you. Not a likely solution in an emergency. After Apple’s Disk Utility refused to help fix the damaged disk I went looking for an alternative. Drive Genius seemed to fit the bill and you can download a DVD boot image and burn it immediately. Imagine that! The internet allows you download large files! Hopefully the other guys figure out that times have changed too.

But while Drive Genius seemed to be a saviour it soon proved itself an also-ran. It gives the same warning messages, the same error messages and the fails in the same places as Apple’s own Disk Utilitiy. So my running assumption is that it is the same. They’ve simply wrapped Apple’s disk repair with their own GUI. If you need a repair boot disk in a hurry and don’t have a Mac OS disk with Disk Utility handy then it’s a good choice, otherwise look carefully at the additional features that it has (which I have not tested) before deciding whether it’s worthwhile.

Hopefully Apple will move to ZFS soon and we can enjoy having some of the dynamic volumes, flexible RAID, and filesystem recovery snapshot features that other OSs are starting to enjoy.

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