I have been using Super Duper to create a bootable copy of my hard drive nightly. (This is in addition to using Time Machine.)
My hard drive has a capacity of 1TB of which 250GB is used.
My backup drive is a firewire 800 WD MyBook 1TB.
I noticed that my backups were starting to take hours instead of minutes and I cancelled the most recent after 19 days.
The logfile says:
| 08:17:26 PM | Info | /Users
| 08:18:53 PM | Info | Ignoring /.hotfiles.btree
| 08:18:53 PM | Info | /bin
| 08:18:53 PM | Info | /Library
| 11:17:40 PM | Info | Disk disk8s2 mount changed!
| 11:17:41 PM | Info | Disk disk8s2 vanished!
| 11:17:49 PM | Info | Disk (null) vanished!
| 12:11:26 AM | Info | Disk disk6s2 vanished!
| 12:11:28 AM | Info | Disk disk7s2 vanished!
| 12:11:29 AM | Info | Disk disk8s2 mount changed!
| 04:49:23 AM | Info | Disk disk8s2 mount changed!
| 04:49:24 AM | Info | Disk disk8s2 vanished!
(more of the same)
I have reformatted the back up drive.
I then tried a USB external drive with exactly the same results.
What's going on? There are no error messages displayed by the OS.
I have contacted ShirtPocket (developers of Super Duper) but no help yet.