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I found my .MobileBackups folder quite large, it weights 160 Gi. Shouldn't the .MobileBsckups folder be wiped after the TM 'backup session'?

Since I have backup done on my external drive how can I get back my 160Gi of hdd space? Can I simply remove this folder or maybe set some limit of mobile backups?

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up vote 20 down vote accepted

There is a lot of confusion as to the purpose of local snapshots. It's not to take snapshots that then get dumped to your actual Time Machine drive when you run a backup, it's a separate set of snapshots that let you restore files you've accidentally changed or deleted, when you're away from your Time Machine drive. It's not a true backup -- it won't help you if your laptop's drive fails -- but it will help out if you're on the go and you accidentally lose something while on the go. As such, they don't get cleared out after TM backups.

On my computer (a Macbook Air with flash memory), it deletes old mobile snapshots after a week. The behavior may be different on devices with hard drives, as they don't experience longevity issues with full disks. According to Apple's documentation, they aren't deleted after a week. Note that the available space shown in Finder does not take into account the local snapshots, because they will automatically be deleted if you need the space, and it will automatically keep at least 20% of your disk space free -- so you generally shouldn't worry about space taken up by local snapshots. However, if you don't want them around, you can disable them with the command sudo tmutil disablelocal. This will free up the space taken by your local snapshots, and if you reenable it with sudo tmutil enablelocal, it'll start again with an empty set of local snapshots. So, a quick way of clearing out what's on there is to disable and re-enable local snapshots.

You can see how many old backups are being stored by activating Time Machine. White tick marks indicate local snapshots, and purple ones indicate real backups.

There's more information from apple and here.

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I found that DaisyDisk is able to get this done if you scan through Admin privileges, I'd suggest you buy the non-appstore version through the site—it's cheaper and has more features.

http://www.daisydiskapp.com

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Removing .MobileBackups using a tool like DaisyDisk is a very bad idea –  George Garside Apr 19 at 20:13
    
Would you please elaborate on this? For the sake of learning and other users who might come across this, please. –  Jonáš Vacek Apr 20 at 20:25
    
.MobileBackups isn't just a folder, it's a mounted volume. Deleting the folder is like deleting a volume from /Volumes — sure you can do it, but OS X won't like it and it'll break many things. Deleting the folder also won't stop Time Machine continue to attempt to backup to it, or stop it looking there for nonexistent backups. –  George Garside Apr 20 at 20:32
    
Well I used this solution to just purge things that must be of no value to me anymore, but wouldn't want to get rid of the feature itself. I understand the volumes bit, is going inside the folder and deleting in there any better or is it just as bad? –  Jonáš Vacek Apr 20 at 20:35
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This is a virtual folder. And displayed size is not actual, there is only changed files copied, but displayed total size of all data. Removing MobileBackups will not make 160 gb more free space.

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