Hello, I have a late 2012 27" iMac with 1TB Fusion Drive. It works great, it's fast and everything, but now something strange is happening. Maybe it's been there from the beginning and maybe it's normal but when i leave my iMac idle, the HDD (not SSD) spins down, i guess to sleep, after a while. But then after a couple of minutes it spins up again and then this continues, it goes to sleep and then starts up again. I have no noticeable issues with the drive, but i just think it's kind of irritating. I've run the disc utility and everything ok. (not that i was thinking anything was wrong with the disk per se) Any thoughts?