Never had a Mac before my new 27 iMac, so I'm not sure what normal behavior is. I'm having problems with sleep disconnecting my external drive. I tried it on my son's Mac Pro. When he clicks the sleep option, it takes 15 seconds or so to shut off the screen, and the same drive is not disconnected. On mine it shuts off immediately. Is this normal? Why the difference? Is it due to the fusion drive?