My automatic backups for my Macs have recently started failing with the following message (same error if I attempt to "Backup Now"):
Time Machine couldn't complete the backup to "DeviceName". The backup disk is not available.
Every other attempt or so I also get a warning that it was a while ago that a backup succeeded. If I open Time Machine Preferences there is a red icon with an exclamation mark next to the backup disk which if clicked produces the following message:
Time Machine Error The backup disk is not available. Latest successful backup: <date>
I just tried to re-select the backup disk from Time Machine Preferences > Select Disk, which worked without problem, but now Time Machine seems to have forgotten all my previous backups (I can still find the backups on disk using Finder, but Time Machine claims that I have no previous backups).
- Now that I have reselected the backup disk, how do I get Time Machine to find the existing backups?
- Is there another way to get Time Machine to find the backup disk?
Setup: One Macbook Air, one Macbook Pro, one Netgear ReadyNAS Duo claiming to be a TimeCapsule. Both Macs use Mountain Lion.