Dear OS X and mac pro Experts, this is a very strange thing: I´ve observed, that OS X seems to power down all HDs in Energy Save mode. That is fine. But when I request a file from HD1 also HD4 seems to be powered up. Now the special hint: HD4 has nothing to do with the requested file: It´s my Bootcamp HD. So my suggestion is: OS X cannot differentiate between single drives, if they are alle from the same manufactor. My setup: 3x 400GB Samsung and 1x160 GB Seagate How can I keep different HDs down - or is the SATA II BUS only ON or OFF at all? Any Ideas? PS: I want to spin down my useless Windows HD to safe energy AND HEAT.