Under MAC OS X how do I spin down my external firewire drive on
demand.  (I have checked the 'Allow hard disks to sleep when possible'
under Energy Saver - but the firewire drive never seems to power
down).

(Explanation: I use this drive for backup; so 23 hours a day it sits
idle. There is no access of data on this drive during the 23 hours. I
have turned off spotlight for this drive - so spotlight isn't
accessing it.   I'm trying to reduce heat - so would like to spin it
down programatically).

Thanks.

PHT

You can just unmount the fire wire disk by ejecting it on the finder.
If You want the firewire be rescanned just go to "About this MAC" Hit
"more Information" and then select firwire.
If you would like to have a more "programmed" behavior you have to
open the terminal.
Type in "diskutil list" all your drives will be shown.
Let's say your "backup drive" is disk1
Then you can easyly eject that drive with "diskutil eject disk1"
If you want it mounted again you type "diskutil mountDisk disk1"
If you just activate the drive with the list command it will not spin
down with eject, because it was not mounted. You always have to mount
a disk to eject it later.