…more than I can tweet…
A few days ago, my MacBook Pro welcomed me with this message:
Time Machine Error
The backup volume is read only
To select a different volume, open System
Preferences and choose Time Machine.
I’d seen this before, and it’s no big deal. The simple fix is to just reboot the Mac, so I that’s what I did. After a 5 second reboot (gotta love these SSD Macs), my Time Machine disk wasn’t mounting, though.
OK, no big deal still, just run Disk Utility to repair it. Disk Utility chugged away on it for an hour or so and then said something like:
Disk Utility cannot repair this disk.
Uh-oh. Now what?
Next up: DiskWarrior. DiskWarrior is a time-tested hard drive repair utility, but I’d been reading that even it often can’t repair Time Machine volumes. Apparently, Time Machine does some pretty oddball stuff with the filesystem that makes it both fragile and difficult to repair, yet somehow more efficient. I didn’t want to drop $100 to find out whether or not DiskWarrior would work on my drive or not, though. It’s just a backup drive, after all. So, I borrowed a friends copy to evaluate it.
My apologies to Alsoft. I know this is outside the license terms, but DiskWarrior really needs a “try before you buy” or demo version. If the demo would have worked, I would have bought it in a heartbeat to be ready for the next time.
Ultimately, DiskWarrior could NOT fix the drive — at least not completely. It first reported that the drive had a hardware failure:
Directory cannot be rebuilt due to disk hardwarefailure (-36, 2541).
Not willing to give up just yet, I dug a little deeper and found this page where Dr. Paul Gardner-Stephen discovered that DiskWarrior will give this and similar “hardware failure” errors if the disk is simply “busy”! Sure enough, a “ps -ef | grep fsck_hfs” revealed the process that was keeping my Time Machine disk busy, so I killed it and tried DiskWarrior again.
This time, DiskWarrior got a little further along in the repair — no “hardware failure” — but it stopped short again with this error:
The Directory of the disk cannot be rebuilt.
There is not enough memory. Restart from the DiskWarrior disc and try rebuilding again. Error code 2154.
Another quick search on Bing (yes, Google, see what you’ve driven me to?) found this discussion on the Apple forums where it seems pretty clear that this is a common issue with DiskWarrior and TimeMachine disks, and there is no workaround.
Again, not willing to give up so easily, I ran Disk Utility again and it appeared to now be getting past the point in the repair process it was getting stuck on before!
At this point, I was exhausted and it was way past my bedtime, so I let it run overnight. First thing the next morning, I checked my MacBook Pro:
My TimeMachine drive was officially back from the dead.