Warning – this tip is fairly advanced. Use it at your own risk.
There’s a feature that debuted back in 2005, called SafeSleep. Basically, it’s a hibernation mode designed to save the current state of your running Mac, so that it can start up exactly the same way you left it when you put the Mac to sleep, even if the battery runs out and it shuts down completely.
In OS Lion, Apple introduced two new features, called Autosave and Resume which mirrors this functionality. Turning off SafeSleep, then, is really just disabling a duplicate feature. It shouldn’t affect Autosave or Resume if you’re running OS Lion or later, and it could potentially save you gigabytes of hard drive space.
Here’s how to do it, though we caution you not to do this if you’re even slightly uncomfortable with the idea.