10-18-2008, 01:12 AM
richorlin wrote:
Maybe I'm missing something, but how does Firewire Target Disk mode help in diagnostics. What could be simpler than booting from an external USB drive and running disk utility on the problem drive, or Diskwarrior if you have it.
Booting from a USB drive does not provide the same utility at all. As was pointed out, if you do so, you're relying on the computer to be in perfect working order other than the boot drive and that's often not the case.
You'd also have to keep at least one spare boot/diagnostics drive on hand all the time and you'd have to be on top of all the latest OS updates to be able to boot the latest Macs.
(With the cables and power supply, that would double the weight of my kit since I'd still have to have either another hard drive or a laptop with FW to support PPC Macs.)
As for DiskWarrior... assuming that you have a version of the CD that can boot that Mac (a big assumption) and all other things being equal (which they're not), it still takes as much as 20 minutes to boot from a DW disc where target mode takes just a few seconds.
But even if it all works out great up until that point, all that it gets you is DiskWarrior. What do you do when DiskWarrior fails? What if DiskWarrior fixes the directory, but then the Mac still won't boot because of some other issue?
You have unfettered access to the contents of the boot drive in target mode, so you can easily (re)move and edit files from the GUI without enabling root. If the drive turns out to have major problems, you're immediately in a position to clone it or to copy important files before trying a dangerous repair or erasing the drive.
On top of that -- for some unexplained reason and only in the last decade or so -- the optical drives in Macs often get flaky when there are hard drive problems.
Target mode is not a panacea, but it's easily half the arsenal for the average Mac tech.
[Edit] Cut out some bad language.