hotplug disk (howto power off)

[nico <nicolasardissono@yahoo.com.ar>]

i have a HP server with 3 hotplug disks, 2 in one array 5 and 1 that i 
use for backup,
the problem is that i cannot power the disk off from debian.
I'm pluging it, use hpacucli and i create the array 0, the kernel detect 
the disk, i mount it, copy all the info, then i umount it and here is 
the problem, how can i power the disk off before i unplug it, now i just 
unplug it, then i delete the array using hpacucli and till now i have no 
errors on the disk but i guess i have to send a command to the kernel so 
it power the disk off or just stop it.
i so that in red hat yo can echo 1 > /sys/block/disk/delete and it just 
delete the disk from memory.

I want to know if what i'm doing is right because the kernel do it 
automatically or if i have to do something, i google a lot and i cannot 
found a solution for debian.

THANKS FOR THE HELP