Mountain Lion: Time Machine Backups Get Very Big!
This weekend I upgraded from Lion to Mountain Lion, and most things work fine. I use an USB hardrive for backups, it's the same volume I used under Lion. Mountain Lion was able to continue using it, so I did not lose the history of my documents. So far, so good.
But: From time to time backups get really big. One example: This morning the backup that finished at 10:30 was about 50 MB at size, which is ok. The next backup started at 11:15 (and is still in progress), and while backing up, the estimated size grows and grows. Currently it's about 26,55 GB estimated, with 24 GB already backed up. But I did not produce more than 26GB of new or changed files, I just visited some websites, read news in Reeder and read some emails with Mail.app.
I saw this behaviour several times since monday, which lead time machine to clean old backups (previously I had backups from March, now the oldest backup is from May). What causes time machine to think that there is so much data not backed up, and why doesn't time machine know the size of the backup before copying the files, as it did in Lion?
Any suggestions?
Marcus
Macbook Pro 15, Mac OS X (10.7.2), 4 GB RAM, 512MB Video RAM. 320 GB Harddrive