To allow hibernate mode, you should have the same mount of free space as physical memory plus 750Mb. Here are possible values: hibernatemode 0 = suspend to RAM only (default on desktops) hibernatemode 1 = suspend to disk only hibernatemode 3 = suspend to disk + RAM (default on laptops) To see your current hibernatemode # pmset -g | grep hibernatemode So, to enable Sleep Safe, open a Terminal console (spotlight search for Terminal) and enter # sudo pmset -a hibernatemode 3 It will ask Read more...