trending at Apple Forums 10.9 won't spin down drives when unmounting them.

This is what I just posted over there...

USB2 Mac mini with TB

I have a Thunderbolt drive and a FW800 drive externally and an SSD internal boot and an additional internal Seagate spinner.

My experience is that unmounting/ejecting several at once will not spin down the drives but they will spin down after the drives onboard inactivity spin down time is reached. If I unmount in the correct order most of them will spin down. Also mounting ANY drive will spin up ALL drives but not mount them. Only the one I chose to mount actually gets mounted. When unmounting the drives I must unmount the Thunderbolt drive last otherwise unmounting any other drive will spin up the thunderbolt drive but again not mount it. The FW800 drive will not spin down at all until it's onboard timer spins it down. Nothing I do will make it spin down any sooner other than writing a script to spin it down which I have not yet tried. (tomorrow.. I'm tired)

Also Temperature Monitor and other temp sensing apps will keep your drives spinning even when unmounted. For some reason Temperature Monitor comes default to poll hard drives for temp every three minutes effectively disabling any spindown timer or sleep function you may be trying to run