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Has anyone seen this issue and know how to fix it?

Look at the free space reported by running "Get Info" on my hard drive (Macintosh HD) in the Finder, "About This Mac" from the Apple Menu, and Disk Utility.

Running on an early 2011 MacBook Pro OS X 10.7.3.

Screenshot of Finder, System Information and Disk Utility

Disk Utility shows:

  • 108.31 GB (108,311,060,480 Bytes) available
  • 390.94 GB (390,937,042,944 Bytes) used.

Finder shows:

  • 206.43 GB available
  • 292,816,503,508 bytes used (292.82 GB on disk).

System Information shows:

  • 108.44 of 499.25 GB free.
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3
  • What version of OS X are you running? They match on my 10.6.8 macbook pro, despite having over 10GB of trash.
    – Adam Davis
    Apr 4, 2012 at 19:22
  • Added to the question.
    – finiteloop
    Apr 4, 2012 at 19:28
  • Having the same issue right after I deleted device backups from iTunes the other day.
    – Joel Glovier
    Jun 12, 2013 at 23:23

2 Answers 2

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16

Most of the difference you're seeing is due to Time Machine's "Local Snapshots" feature. When Time Machine is turned on but the backup device isn't available, it backs up to the local volume. The space used for these local snapshots is counted as "in use" by Disk Utility and System Information, but not the Finder (see the Disk Space considerations section of this article). While the space for backup actually is in use, it'll be freed automatically when needed (i.e. when the volume gets above 80% full), so the Finder counts it as being available.

In your particular case, the space System Information lists as being used for "Backups", 98.36GB, is very close to the difference in free space listed by the Finder vs. the other two. The Finder's 206.43GB free - 98.36GB of backups = 108.07GB actually free; compare to System Info's listing of 108.44GB free and Disk Util's 108.31GB. I'm not sure what the rest of the difference is (maybe they looked at the disk at slightly different times? Or they may be counting volume structures a bit differently?), but it's very small.

Finder shows:

  • easily, the truth for JHFS+ volume Macintosh HD
  • optionally, the truth for mtmfs volume MobileBackups

Hint: with local snapshots enabled in Time Machine, in Finder you can go to /Volumes/MobileBackups then get info.

Results of a one-line command show that for some purposes, MobileBackups is treated as a distant file system: 

qlmanage -m disks | grep MobileBackups && mount | grep MobileBackups

As Disk Utility is oriented to local file systems, we'll probably never see MobileBackups as a separate volume in that context. There are degrees of simplification in Disk Utility, even when debug options are chosen.

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  • This seems to be the correct answer. Performing a backup (first in 4-5 days) seemed to decrease the difference significantly. I'm not sure how to feel about this new 'feature' of lion. It makes me uncomfortable that I don't have a good understanding of the contents of my Hard Drive. Is there some way of turning off this local snapshot feature without sacrificing the functionality offered by versions and time machine?
    – finiteloop
    Apr 10, 2012 at 23:14
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    @segfault: Yeah, between Spotlight, Versions, and TM local snapshots, Apple's adding a lot more behind-the-scenes magic into their filesystems. In the case of local snapshots, you can turn them off with `sudo tmutil disablelocal' -- I haven't tried it, but I think that'll recover the space currently used, as well as disabling future snapshots.
    – Gordon Davisson
    Apr 11, 2012 at 0:28
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    Great! This disabled local snapshots, and after a restart fixed the difference in space between all 3 applications. They now agree. I think Apple is screwing up with this. It is a nice feature to have, but the way it is implemented makes people who know their way around a computer (like myself) very uncomfortable.
    – finiteloop
    Apr 11, 2012 at 1:26
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    The "local snapshots" link no longer goes to the correct place; here's the relevant KB article: support.apple.com/kb/HT4878
    – daGUY
    Jul 24, 2013 at 15:35
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It looks like Lion changed a few things about disk space management, and you're not the only person with this issue and likely related issues. Some are reporting that doing a shutdown and restart resolves the discrepancy. Others indicate their disk space discrepancy had to do with Time Machine's local backup feature on laptops.

Do a full reboot and see if that resolves the problem. If not, disable local backups, then do a full reboot.

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  • your answer is correct, however because of the depth of gordon's response, I selected his as the accepted answer.
    – finiteloop
    Apr 11, 2012 at 1:27

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