I have a 2009 iMac into which I self-installed a Fusion drive, using widely available instructions (about a year ago I guess). I waited until the Mountain Lion update came out that had full support for self-made Fusion drives. Everything works great except one thing: sometimes, when I put the machine to sleep, it wakes up a second later, does something briefly, and then goes back to sleep. This might happen several times before it finally stays asleep. Just now, it happened like 20 times and that led me to post here. Although I have no direct proof, I can't help thinking that the Fusion drive installation is what started this problem. Anyone ever heard of this, or know a way to diagnose it?