>One very annoying thing though is that the disk driver waits for a
>long time after resume for some DRQ, and then spins up:

I don't believe this is the fault of the disk driver, per se.

As everyone knows, there is a lot of variation between APM BIOSes on
different machines; the same holds true for IDE disk powerdown
implementations.

There are three powerdown states for IDE disk; idle, standby, and sleep.
Both idle and sleep have to be entered via explicit commands, and
you set a timer for standby.  This is the way it's supposed to work, but
it's not always the case.  For instance, my Toshiba disk doesn't implement
idle at all, and if you set _any_ timeout in the BIOS for sleep, as soon
as it goes into standby mode it really sleeps (which implies there's
some undocumented Toshiba sleep timer, but I don't know what it is).

Standby mode is generally where the disk spins down, but still responds
to commands.  Sleep is where the disk shuts off completely, and requires
a reset to reactivate.  Those error messages you're seeing are indicative
of your drive going into sleep mode; the command tries it, the driver
issues a reset, and everything continues along.

I don't know about your machine specifically, but you might try playing
with BIOS settings for standby and sleep.  Also, if you have a fairly
current -current, try seeing if atactl(8) helps you out in any way.

--Ken