I have a few different backups on my desktop mac running 10.8.3 - time machine, carbon copy cloner, and crashplan.
A few days ago, I needed to reinstall my OS for a separate problem with iPhoto that is now resolved. However, after a few days, I noticed that TM had not performed any automatic backups - CCC and CP still backed up normally.
I verified that TM was still on and my backup disk was still correct in System Pref. After selecting "backup now", I noticed that TM will go thru a prolonged period of "preparing for backup" and then stops - without any backup occuring and no error message appearing.
In looking thru the Console log, I consistently see a problem where my backup disc is ejected during this process. I backup to a Drobo external HD that has gone thru a cycle of HD upgrades over the years and, per the Drobo Dashboard software, is performaing normally.
The messages in the Console logs usually involves a "deep event scan" - then some other messages signalling data being copied or old backups being deleted to clear space. Then, there is a message "stopping backup to allow destination disk to be unmounted or ejected", followed by "Cancellation timed out - exiting".
Occasionally, I see a message in TM that backup will continue when the disk is available - although it is clearly mounted in the Finder and I can access the data on it manually.
According to Drobo, I have over 1TB free on my backup volume and Console mentions it needs 650GB (incl. padding).
The old backup data on Drobo is still present and accesible, so I hate to start a fresh backup and lose what's there - although I do have redundancy.
Any help would be appreciated - Thanks!
Tried a couple of things further after going thru some posts and solved the problem with unchecking "put HD to sleep when possible" in the Energy preferences.
I never have this selected on my systems but it must have been checked by default after the sysem reinstall that triggered this problem.
However, it is curious that Apple allows this problem to occur. Since the OS know that TM is backing up to the external HDs (it's destination is selected in System Pref), and the Energy Pref is to put HD to sleep "when possible" - why is the OS allowing the TM backup HD to go to sleep when it is not possible to do so, since going to sleep obviously triggers this error of stopping the TM backup to allow the destination disk to be unmounted???
Seems a stupid oversight by Apple...