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10.4: Recover a dead hard drive using GNU ddrescue
Authored by: paulhagstrom on Jul 21, '07 03:09:56PM
Just wanted to add a note here: This also works well with floppies. I finally decided to image all of my floppies and then throw the floppies away, given that most of the media is over a decade old. It went pretty well using Disk Utility's disk image creation, but where a disk had a bad sector on it, DU refused to do anything with it. This ddrescue program did a nice job of preparing me to use DiskWarrior to repair. I still have only DiskWarrior 3.03, on a PPC machine, and there are some issues with the preview mode, but I've found that if Classic is running, DW seems to work. Who knows why, maybe it's just superstition, but I don't think it is entirely. Anyway, I did the following, in the terminal:
  • Insert the disk
  • df
  • Locate the floppy drive, say /dev/disk6
  • If the floppy mounted, unmount it by:
    diskutil unmount disk6
  • Run ddrescue:
    ddrescue -v /dev/disk6 ddr_sda159.dmg sda159.log
  • Eject the disk:
    diskutil eject disk6
Then, mount the resulting image (ddr_sda159.dmg in this example, double-clicking on it will do the trick), switch over to DiskWarrior, rebuild, preview. Switch over to Disk Utility, select the rebuilt volume (with the DW icon), convert the image. Back to DiskWarrior to cancel, and then finally unmount the original image. It worked quite nicely for those disks that had only a tiny amount of damage. I haven't had any that actually didn't mount at all, so parts of this procedure may need to be tweaked for that scenario. Specifically, the part where I mounted the disk image that ddrescue produced might not work in that case, and it would probably require using hdiutil attach -nomount to get it to be visible to DW, something like this, though I haven't had a need to try it:
hdiutil attach ddr_sda159.dmg -nomount

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10.4: Recover a dead hard drive using GNU ddrescue
Authored by: paulhagstrom on Jul 21, '07 03:17:03PM

Let me just add one thing: The reason I didn't use DW on the floppy directly is because it flipped out in various ways, spontaneously unmounting things causing the Finder to complain about unorthodox device removal. I did try that first. What I like about this recipe is that it gets as much off the disk as the drive is capable of and then I can play around with whatever recovery tools I want on the image.

One thing that I am not confident of is that DW will detect if there was an error in the middle of a file's data, my guess is that it won't. So, it's still probably necessary to treat the recovered files as being only possibly working.

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