I have updated to Mountain Lion on Mac Mini (mid 2011), and now my Mac is very slow after sleep. I am waiting for several minutes before the next selected program is working properly.

I have tried:

  1. resetting SMC,
  2. check disk and permissions,
  3. disable disk hibernation but have no result.

When I put it to sleep manually everything okay (in 1 minute), but when it going sleep by timeout I have hyper-lags and slow and low-low-low performance.


I recommend you start 'Activity Monitor' (found in Applications/Utilities') before you let the Mac go to sleep. If an Application shows a high CPU-load it could be the culprit.

In you case it's probably the 'Safe Sleep' function, the equivalent to the Hibernation Mode in Windows, which creates a temp. file on your HD to ensure a correct wake-up - even after a power loss. The file is usually the same size of the RAM and is probably the cause of you problems.

Can you give more details to the RAM- and HD-Size?

Edit: if you check your activities as i mentioned before, did you notice any activity in /var/vm/

There should be a file called 'sleepimage', which you can remove. It will be rebuild if needed.

You should check your Power Management Settings in the Terminal via pmset

pmset -g | grep hibernatemode

The default should be "hibernatemode 3", meaning that RAM contents is written to the disk upon sleeping. To test if the reading of the sleepfile is causing your sluggish behaviour you can disable 'safe sleep' with

sudo pmset -a hibernatemode 0

Please try that and post your observations.

  • Sure. I have 5gb ram and 425gb free disk space (HDD) – Roman Truba Oct 23 '12 at 2:27
  • Did you have a chance to check you setting as described above? – J.C. Nov 5 '12 at 9:42
  • I set sudo pmset -a hibernatemode 0. Now it have undefined behaviour. It can be slow once, but next time it is okay. I can't understand it... – Roman Truba Nov 5 '12 at 16:18
  • @RomanTruba, I was experiencing the same erratic behavior on my Retina MBP. I believe I found the regularity. If I delete the hibernatefile (/var/vm/sleepimage in my case), the MBP wakes up instantly after sleep. However, restarting the MacBook creates the file anew and then causes sluggish wake-up behavior. – Alex Dec 19 '12 at 15:58

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