SuperDuper scheduled backup is taking down my whole system...

[Marco_Polo]

I figured it out.

It was a statistical fluke.

The backup drive is in one of those horrible Seagate enclosures that is designed to save energy by putting the drive to sleep even while the drive is being accessed.

I had long ago disabled that "feature," but the device appears to have decided to start sleeping the drive again at seemingly random times that just happened to coincide with my backups. My NAS still thought that the drive was still spun up, thus the "phantom" drive icon that would show up when the scheduled backup began.

When I swapped the drive into a new enclosure the backups resumed again without fail.

Thanks for your help.

BTW, One criticism about SD's behavior through this: The application locked up and couldn't be quit when the volume failed to mount correctly. SD ought to have some sort of timeout under this circumstance, logging an error and allowing me to quit it.