TimeMachine mobile backup eats up disk space if backup drive unavailable
Apple introduced a new feature called “mobile backups” with OS X Lion.
The idea behind that: Use a temporary part of the local hard drive to store backups until the backup drive is connected again.
True, this is a good feature for most. But if you can spare some backups, because you – let’s say – store your files to a dropbox folder, which is synchronized to a cloud service, then you may not need the mobile backup feature of OS X.
In fact, you may notice running out of disk space, that you could use otherwise.
So to see the difference, let’s check out the available free disk space in Termin us the ‘df’ (disk free) utility:
gianpaolo-del-mattos-macbook-pro:~ Gianpaolo$ df -h Filesystem Size Used Avail Capacity Mounted on /dev/disk0s2 79Gi 69Gi 9.1Gi 89% / devfs 129Ki 129Ki 0Bi 100% /dev map -hosts 0Bi 0Bi 0Bi 100% /net map auto_home 0Bi 0Bi 0Bi 100% /home localhost:/SkA_FxsNwtVofJZZOc308I 79Gi 79Gi 0Bi 100% /Volumes/MobileBackups
Gosh, I’m almost out of space, having only 9 Gigs left :-/
So let’s get rid of the mobile backups using this command:
sudo tmutil disablelocal
Now check back at the disk space:
gianpaolo-del-mattos-macbook-pro:~ Gianpaolo$ df -h Filesystem Size Used Avail Capacity Mounted on /dev/disk0s2 79Gi 60Gi 18Gi 77% / devfs 129Ki 129Ki 0Bi 100% /dev map -hosts 0Bi 0Bi 0Bi 100% /net map auto_home 0Bi 0Bi 0Bi 100% /home
You notice, that the ‘/Volumes/MobileBackups’ mount point is gone?
I’m having 18 Gigs free now as well.
So, depending on how long you didn’t have your backup drive connected, the amount used may well increase to a multiple of that.
It may not be best choice for most people to have mobile backups disabled. But if you DO know what you’re doing, then go for it 😉