Address available hard drive space skyrocketing after installing OS X 10.10.3

HardDriveIconXAn issue may occur on some Mac systems where after installing the OS X 10.10.3 update, the Finder and other services that report drive space may show an increasing level of available space. This may be accompanied by the Storage tab in the About This Mac window showing your hard drive’s space is being used only for backups.

In general, when this type of oddity appears in the About This Mac window, it suggests your drive’s Spotlight index needs to be rebuilt; however, this issue will likely survive a forced index rebuild. In addition, it being mirrored in the Finder’s status bar and information windows suggests the issue is not with Spotlight, but with another aspect of the system, namely Time Machine and the way that local snapshot backups are being handled.

Time Machine is primarily intended for use with an external storage drive, so large full-system backups can be maintained; however, it also supports a smaller local snapshot database that is stored on your boot drive. These local backups allow Time Machine to provide similar backup services for personal documents you create, when you do not have your dedicated Time Machine drive attached to your Mac.

Local snapshots are stored in separate backup instances in the same Backups.backupdb structure as a dedicated Time Machine drive; however, in this latest problem, affected systems are including a size calculation from each new local Time Machine backup instances in the Mac’s available space calculation. This may be the free space on the drive at the time of the backup, or otherwise, but it ultimately results in a progressive increase in the calculated available space, which may get up to many hundreds of terabytes or even petabytes in size.

This problem will likely need to be fixed by Apple’s engineers; however, you can attempt to override the issue by disabling local Time Machine backups:

Incorrect available space calculation in OS X

The terabyte calculation for available space on the drive is incorrect.

  1. Open the OS X Terminal utility (in Applications > Utilities) in an administrative account
  2. Run the following command 
    sudo tmutil disablelocal

This command will not only disable the creation of local backups, but will also delete any that are on your system. This action should clear up the incorrect free space calculation on your Mac; however, if re-enabled by repeating the command with “enablelocal” as the final term, the problem may start up again.

With local snapshots disabled, you can still use your standard Time Machine drives normally to create and update your backups. The only difference is that Time Machine will require the presence of your backup drive to create backup versions of your files. For the most part, this will only cause a minor inconvenience if you want to access files that are automatically backed up by Time Machine. Otherwise, it will make no difference in how your Mac runs. You can also re-enable local snapshots at any time, if needed.

3 thoughts on “Address available hard drive space skyrocketing after installing OS X 10.10.3”

  1. Carlos Cardona

    Is that “disable-local” with no spaces? When there’s a hyphen at the end of a printed Unix command it’s confusing, isn’t it? Is it a line break hyphen, or a hyphen in the command? Is there a space after the hyphen, like “enable SPACE Hyphen local” (like so many other commands?)

    Thanks-Topher! 😉

  2. Carlos Cardona

    OK, I tried it, and it’s “enable SPACE -local” right? Without the hyphen you get “unrecognized verb”!

    1. Strod

      Carlos, I see it as:
      sudo tmutil disablelocal
      with no hyphens or ambiguous spaces. (My guess is Topher may have fixed it).

      Anyway, you can verify the syntax of this and almost any other Terminal command by checking its man page:
      man tmutil
      Scroll down to the <bVERBS section and you will find, among many others, disable and disablelocal. As you will see, the first one disables all automatic backups, even when the external backup volume is mounted. What you want is to disable only the local backups, achieved with the second “verb”.

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