Time machine not backing up to full disk

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Level 1

45 points

Time machine not backing up to full disk

My backup disk recently filled up. Now I get a message saying:

"Time Machine couldn’t complete the backup to "Backup disk." The backup disk ran out of space unexpectedly. Time Machine will try to make more space available by removing expired backups during the next scheduled backup."

When I then manually click on "Back up now", it runs fine. But then an hour later the same thing happens. I thought that with a full backup disk, Time machine is supposed to automatically make space by dumping the oldest backup...

Thanks!

Dan

iMac, OS X Mountain Lion (10.8.2)

Posted on Oct 13, 2012 8:17 PM

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Answer 1

markwmsn

Level 6

15,029 points

Oct 13, 2012 11:33 PM in response to DanK

Probably indicative of a Time Machine target disk too small for the task.

How large is your Time Machine disk compared to the sum of the sizes of the disks it is backing up? It should be two or three times as large, maybe more.

Do you have any very large files that change often being backed up (e.g., virtual machine images)? If so, increase that ratio.

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