The hard drive on my iMac failed last week. I'll spare you most the details, but suffice it to say Disk Utility couldn't bring it back and a fresh install wouldn't work. I tried everything. Trust me. Luckily it was covered by my Apple Care protection plan so I took it to my local Apple Store and they replaced it without a problem.
I wasn't too concerned about replacing my data since I was using Time Machine to backup my iMac. When I get home I start up my computer, proceed to restore from backup, and find that my Time Machine backup volume cannot be mounted.
This is when I start to get worried. Apple's Disk Utility reports success on verify disk but fails on repair disk. Damn. Same thing from the command line using
fsck_hfs and from Recovery mode.
What are the chances that my main drive and my backup drive have a similar failure in the same week? I'd say pretty good.
Recovery Attempt #1
I purchased a recovery utility called DiskWarrior, which was ultimately no help. The app, when run from OSX, has memory problems when repairing a drive larger than my pinky finger. I'm still waiting to receive their rescue CD to see if the drive can be repaired when booting from that, but I'm not holding my breath.
Update 1: I tried booting from their rescue CD and received the same error message.
Recovery Attempt #2
My next step was to find and use a tool called ddrescue. Its a modified version of the unix
dd utility that does a better job when copying bad sectors. This took forever, but at least you can interrupt and continue the process later if required. I ended up stopping this part of the way through because I was concerned that my target drive wouldn't be large enough to hold the full disk image. Both were 2 GB in side, but I had an OS and other files on my main hard drive.
To The Cloud!
Luckily I had a backup of my backup using CrashPlan. I made an initial download of some important files and that seemed to work ok. The download speeds are slow, but its better than being without 50 GB of family photos.
One thing that helped the recovery process was the fact that a lot of my day-to-day data was in the cloud. My bookmarks and contacts are stored in iCloud, and all my passwords are store in Dropbox ala 1Password.
Don't cheap out on your backup hard drive. I'm going all-in and replacing my external USB drive with a Drobo 5N. I'm going to disassemble a Linux file server box that I have and use those drives plus a couple new drives to create a single, safe file storage solution.
Time Machine corruption is very hard to fix. This is due to the way Apple creates and versions each file of the backup. Make sure your Time Machine drive is reliable and always in good working order.
Keep the important stuff in the cloud. I'm glad I used CrashPlan. I may ultimately switch to using Amazon's Glacier service, but either way keep an "oh shit" backup somewhere online. Even if its a smaller than a full system backup.