>On the i386 there's APM to stop the CPU and IDE disks and control
>battery on a laptop, but is there any way I can spin down my SCSI disks
>after a certain amount of idle time and have them spin up again when
>accessed (to save power of course). 

APM really has no concept of what the disks are doing.

The way IDE works is that you tell the drive, "Spin down after N seconds
of no accesses".  The operating system doesn't know that the drive has
been spun down.  We now have a userland utility to set that timeout on
the drive, but NetBSD really doesn't know if the disk has been spun down
or not.

There should be enough accounting in the kernel to have NetBSD do it
(which would also work for SCSI drives), but no one has yet written
it.

--Ken