external harddrives - do you turn them off even when your computer shuts down?

[dionx]

i want to preserve my new external harddrive. is it beneficial to shut down the harddrive when not in use or do they have some sort of automatic sleep mode that i don't know about?

i've got a Western Digital 320GB External.

 

[GnomeCop]

mine doesnt have an auto sleep mode as far as I know, so I just turn it off