A portable Mac using Lion and Time Machine creates local snapshots of new and modified files when it cannot access its TIme Machine drive. These local snapshots can be used to recover deleted or mistakenly modified files. They take advantage of unused space on your hard drive and adjust according to how much space you have available.
Hi, this is Gary with MacMost Now.
In today’s episode let’s talk about Time Machine Local Snapshots.
So, Local Snapshots for Time Machine is a special feature of Lion and only applies to portable Macs: MacBooks, MacBook Pros, MacBook Airs. If you’re using Time Machine to back up to external drives or to Time Capsule, now what happens is, when you’re not connected to that drive, you’re still going to save your hourly backups of changes, files that have changed, to a local partition on your drive. That way, if you accidentally delete a file or want to revert to a file that you had yesterday, or just a few hours ago, you can do so even if you’re not connected to your Time Machine backup. It doesn’t back up everything like the regular Time Machine backup would, it just backs up the files that have changed since the last time you did a major back up to your external drive. Let me show you.
So, here’s my MacBook Air. If I go up to the top of the screen and I click on the Time Machine icon, I can see that the backup hasn’t been performed for a while, says September 10th, that was days ago, it says Backup delayed, don’t tell me that, it’s because the device, the external drive in this case, isn’t connected.
Let me enter Time Machine anyway and take a look here. And it will go to just a folder, my Desktop folder in this case. Now on the right I see all the different time I can jump back to. Even though the external drive isn’t attached, I can still jump back to one of these because I have a Local Snapshot of it. So let me jump back to earlier today and I can see that there are actually a couple of folders there on my Desktop that aren’t present now and I can actually dig into those and recover something.
Now, you may have noticed that if you go into your System Preferences and go into Time Machine, you’ll see this section right here that talks about: Time Machine keeps Local Snapshots if space permits, so you won’t see this if for some reason you are not keeping local snapshots, like for instance if it’s not a portable Mac, if it’s a desktop Mac, that won’t appear.
Now another thing to keep in mind is local snapshots are very silent. You don’t see the Time Machine working, it doesn’t show that it’s backing something up, it doesn’t record that the last backup was on a certain time if it was a Local Snapshot, only if it’s the actual full backup to an external drive, so you may not even know that this is happening.
Now I’ve just attached the external drive that were* into my Time Machine Backups and it hasn’t started a backup yet, but I’m going to jump into Time Machine now and I’m going to see something a little different. Looks like before, but on the right you notice I’ve got some times here in pink and some that are in grey. The pink ones represent full Time Machine backups that are on the external drive. The grey ones represent Local Snapshots that are in between those times.
So basically what the Time Machine Local Snapshots is doing is it’s trying to use the unused space on your drive in a smart way. So, yes, it’s going to take up extra space on your drive, but only if you’ve got that extra space. So if you’re short on drive space, it’s not going to perform the local snapshots, furthermore, if you start to run short on space it’s going to be removing the local snapshots, as the matter of fact it’s always kind of condensing them, right it’s going to save the hourly ones for today, but eventually it’s going to combine them into dailies, weeklies and monthlies just like regular Time Machine and as you run out of space it’s going to get rid of them, and as a matter of fact, if you run really low on disk space it might stop using Local Snapshots all together.
So this means that you can’t monitor your hard drive space too closely when you’re using Local Snapshots. For instance, say you have a 10 gig file, really large video file. Well, that’s going to get backed up to Local Snapshots, so you have a second copy of 10 gig file that you don’t even know about, so it’s 20 gigs of space. As long as you have plenty of space, that’s fine. Delete the file and now you’ve freed up 10 gigs of space, but the Local Snapshot version is still there, of course it’s got to be there, because it’s there in case that you accidentally deleted that 10 gig file and want to recover from it. Then, later on, when it gets too old, it’s removed from Local Snapshots. That means that suddenly you get 10 gigs of space back on your hard drive, the second copy of that file that the Local Snapshots was keeping.
You can see exactly how much space is being used, by going to About This Mac, More Info, and then if you click on Storage you’ll see this chart here. Now, one of the pieces of this chart is the little purple Backups – that’s your Local Snapshots. In addition, you can even see where your Local Snapshots are kept so in the Finder you want to go and you can’t actually see this line, unless you Go To Folder and inside you go slash volumes, like that, and what will happen is, it will bring up the volumes connected which is Macintosh hard drive and lo and behold another partition called MobileBackups. If you look in there you’ll see a Backups file, of course you shouldn’t mess with that, you should just leave it as is, but it’s interesting to know where it’s keeping it.
Mac can also disable Local Snapshots if you really want to. Per se* if you need to do video editing or sometimes need large files appear and disappear from the drive you may want to do this. The way you do it is in Terminal, is use this command here and you can use enablelocal to turn it back on. Now when we disable Time Machine Local Snapshots it’s not going to get rid of them all immediately, it will actually take some time to go through and clean up the Local Snapshots, so don’t expect to see the space return that second.
Also know that if you look at the file space available in the Finder, the amount available on your local drive, it won’t take these backups into account. That’s because they are free space and can be reclaimed by the system if needed. So if you have, say, 10 gigs of Local Snapshots on your drive with 90 gigs remaining, it will show up in the Finder as if you have a hundred gigs of free space.
And Local Snapshots also work for external drives so if you carry a portable external drive with you and you’re using that while on the go, it’s going to store a Local Snapshot of files that have changed on that external drive. It won’t do it in the same way as the partition, it actually creates a folder for that, but it is done.
That’s a look at Local Snapshots. Now a lot of people may feel that right away they just want to turn this off and I really recommend against that, unless you’re having some sort of hard drive issues or something, I would just leave this on. It’s a really good use of that unused disk space on your drive and if you’re short on space it’s not going to get in the way. Till next time, this is Gary with MacMost Now.