For quite a while now I've not been able to get my hard drive to sleep on my 3.6 ghz i5 iMac running 10.7.3. It just continues to run when I put the computer to sleep and the fan runs at normal speeds as well. This is evident when waking the computer back up when the computer starts up quick and there is not hard drive spool up that I notice on the same iMac my parents have. All the proper settings in the energy saver are clicked to make sure the hard drive should sleep along with the display but no luck. I looked into my active processes to see if something was holding it up but I can't seem to find anything. Here's a picture of my processes that are running...anything look suspect? Anyone have any other ideas? Thanks for your help.
Notice that in System Preferences, Energy Saver, that the option clearly states "Put the hard disk(s) to sleep when possible" That should tell you that not all hard drives can be put to sleep by the system. Check with the drive manufacturer to see if there is a firmware update for it that might address the problem.