Hi guys! Ran the Yosemite Beta and GM and never had this issue. Well, I did a nice and clean install the other day for Yosemite and am now having a weird issues with my external hard drive (WD My Book). I can constantly hear it being accessed (spinning) when absolutely nothing is going on. Usually when no access is occurring, like normal, it sleeps until being accessed again. The only way to silence the bloody thing is to unmount it. I've went drastic and even formatted it, still, the issue persists. Any thoughts on this? Advice or tips to try to make this thing sleep when not in use? Thanks all!