I have an SSD as my boot disk on my 2010 MBP 13, and an HD in the optical slot used just for data. I love the stillness and silence of having the HD spun down. Problem: after using Disk Utility to Unmount the HD, all is fine. The disk is spun down, and stays that way. Then I close the laptop for a while, open it back up -- and voila! the HD spins up again, and stays spun-up. There's nothing on it being used. The only way I've been able to get it to spin-down again is to get into Disk Utility, mount the disk, then immediately unmount it again. Obviously, I don't want to do this every time I open up the laptop. Ideas? I'd be happiest if the internal HD didn't get mounted at all on boot, leaving me to mount it manually when I need it, but I'm not sure how to do that.