Putting hard disks to sleep via script?

[haravikk]

Hmm, because of a RAID card I've added (RocketRAID 4310) it seems I have to disabled the "Put hard disk(s) to sleep whenever possible" feature in Energy Saver, as if the card's volume is ever put to sleep, it never wakes and the whole system crashes down, well, if the volume is the startup disk anyway, which it is in my case.

However, I also have three external drives, and it'd be nice if these would still go to sleep, but the feature appears to be a system-wide thing, either all drives have sleep enabled, or none do.

I'm wondering if there are any other options for this? For example, my largest external drive is a time-machine backup, so it'd be nice if it only spun-up when the backup begins, then spins down afterwards, any way to do this?