Apple’s ‘Safe Sleep’ is a major factor for iBook, MacBook and MacBook Pro hard drive crashes. When the user closes the lid with the system still on, they are expecting that the system is entering a sleep mode by powering down the hard drive and just uses enough power necessary to keep the memory contents stored in RAM. However, this is not what is actually happening. Instead, the system takes the time necessary to save the contents in RAM to a file on the hard drive, just in case the system runs out of power while in suspend mode.
In theory, the intent is to help avoid losing critical data in files that might still be open when the user closes the lid. Unfortunately, the end result is that the user is not aware that it can be taking several minutes for the memory contents to be saved to disk, thus causing the hard drive to remain spinning while the system is being moved around with less than necessary caution.

To avoid causing damage to your hard drive, you can either wait for the system to completely power down the hard drive. This is shown when the LED in the button which releases the lid is slowly pulsating on the Mac Book. The other option is to disable Safe Sleep all together.

Instructions to disable Safe Sleep *

Using the Terminal program, run the following two commands:

$ sudo pmset -a hibernatemode 0
$ sudo nvram “use-nvramrc?”=false

To free up the hard disk space used by the sleep image file:

$ sudo rm /private/var/vm/sleepimage

To re-enable Safe Sleep

$ sudo pmset -a hibernatemode 3
$ sudo nvram “use-nvramrc?”=true


If your hard drive has crashed and you experienced data loss with your iBook, MacBook or MacBook Pro because you were not aware of the Safe Sleep functionality, you are not alone. To find out more about how Recovery Force can recover data from an iBook or MacBook hard drive, go to our Apple Data Recovery Services page or call 866-750-3169 to talk to one of our data recovery team members.

* The information in this article explaining how to disable Safe Sleep is found at macoshints.