Capacity shown on Macbook incorrect

fjon

I noticed over the last few days that the capacity on my Macbook Pro is about 20GB bigger than it was. I haven't deleted any significantly large files recently, so not sure where this is coming from.
If I look at the Status Bar in Finder it shows about 114GB free.
If I click "About this Mac" and "Storage" though it shows only 41GB free.
Anyone know what's up, and how I can fix it?

Banta

Sounds very strange.

If you open up "Disk Utility" and click on the hard drive (e.g. Macintosh HD), what does it says in terms of storage/free space (it'll be at the bottom once you click on the hard drive)?

fjon

Banta wrote: »

Sounds very strange.

If you open up "Disk Utility" and click on the hard drive (e.g. Macintosh HD), what does it says in terms of storage/free space (it'll be at the bottom once you click on the hard drive)?

Thanks for the reply. That one also shows 41GB. It looks like the number in Finder is incorrect then?

Banta

When this occurs (I've only seen it in person once, but read it occuring a few times online), it's usually to do with Time Machine.

If you go to About This Mac and look at the storage, can you see "Backups" taking up a lot of space? i.e. the difference difference between the 2 readings?

Banta

Found this, after a bit of searching: http://support.apple.com/kb/HT4878

So it could be just to do with the local "snapshots" as they're called. Nothing to worry about it appears,

"If your disk is low on space, Time Machine stops creating new snapshots. Some or all snapshots may be removed to make space available for applications to use. If sufficient disk space becomes available again, Time Machine resumes creating local snapshots."

fjon

Banta wrote: »

Found this, after a bit of searching: http://support.apple.com/kb/HT4878

So it could be just to do with the local "snapshots" as they're called. Nothing to worry about it appears,

Oh gosh, I didn't get any notifications of these replies and didn't think to check on this! I looked at this, and the backups is showing pretty much the difference between the two readings.
Thanks for the research on this. I'll try to read up more on it and see if I can find out more. It looks like they are taking up a lot of space.

fjon

So it seems I may have fixed the issue, but I'm not sure how!
I went into Time Machine preferences, turned Time Machine off (which would turn off local snapshots), and then when I turned it back on the two numbers are now showing the same number.
Not sure how this fixed it, but Banta was correct in saying it was related to this!

cython

fjon wrote: »

So it seems I may have fixed the issue, but I'm not sure how!
I went into Time Machine preferences, turned Time Machine off (which would turn off local snapshots), and then when I turned it back on the two numbers are now showing the same number.
Not sure how this fixed it, but Banta was correct in saying it was related to this!

By switching off time machine you probably triggered your macbook to nuke all the local snapshots, and then when you reenable they're gone. They will probably build up again over time though.

fjon

cython wrote: »

By switching off time machine you probably triggered your macbook to nuke all the local snapshots, and then when you reenable they're gone. They will probably build up again over time though.

Oh no Is there any way to turn them off? And should they really take up that much space (<25GB)?

cython

fjon wrote: »

Oh no Is there any way to turn them off?

Turn off time machine

fjon wrote: »

And should they really take up that much space (<25GB)?

As per the link that Banta provided,

Do local snapshots take up disk space?

Time Machine is designed to store local snapshots only when there is plenty of free disk space on the startup disk. This means that you can keep using your available disk space when you need it.

If your disk is low on space, Time Machine stops creating new snapshots. Some or all snapshots may be removed to make space available for applications to use. If sufficient disk space becomes available again, Time Machine resumes creating local snapshots. This means your disk has the same amount of available usable space as it would if Time Machine were not enabled. Time Machine uses the rules below to determine whether to stop creating snapshots, or to remove existing snapshots.

less than 20%
free disk space When your startup disk free space is less than 20% of its total available space, Time Machine removes snapshots starting with the oldest one first. It then removes newer snapshots as needed, saving the most recent snapshots to remove last. If more than 20% of the drive space becomes available again later, Time Machine stops removing snapshots.

10% to 20%
free disk space If your startup disk’s free space falls below 10% of its total available space, or is less than 5 GB, the task of removing snapshots is given a higher priority on your Mac. When free space is between 10%–20% of total available space, removal continues at a normal priority.

less than 10%
free disk space If Time Machine is unable to free up enough space to reach the 10% or 5 GB threshold, Time Machine removes all snapshots except the most current one, and stops creating new snapshots. Once free space rises above this threshold, a new snapshot is created, and the previous one is removed.

So basically this space may end up getting chewed up again as long as you have time machine enabled, but this is not really an issue as they are only making use of space that you have, and the space will be freed as required if/when an application requests it. To my reading, this sounds broadly like the memory management in many *NIX OSes, whereby they will use idle memory for buffering and caching. In the same way, time machine is trying to transparently use your empty disk space in such a way that it provides you a level of backup capability with space that would be otherwise unused. Given that disks are a bit more subject to wear and tear than RAM it may have its issues, but ultimately if you want to use time machine, you will accrue them, otherwise switch it the hell off.