Last October I wrote about my system disk backup strategy. Yesterday I had occasion to put it to the test. For some unexplained reason, my nightly backup (cloning the system disk) threw a number of hard disk read errors. Booting into my system clone, and running the disk utility repair task on my original system disk gave me the disheartening news that the disk was not repairable.
Since the clone seemed to be running OK, I erased the original system disk, and cloned the clone back to it (if that makes sense). Then I grabbed a demo copy of Drive Genius 3 and had it run a full read scan of every block on the original system disk. It passed with no errors.
My conclusion is that the hardware/drive is OK, but some software component went berserk and damaged blocks on the disk, or maybe I did something bad with a reboot/emergency power down.
In any event, it was a fairly painless recovery with just a few preference adjustments on the new system.
