Backup noobie, multiple external drives, hand-holding?

[cococello]

Hi, I've searched through as many threads as I could find regarding using SD to back-up multiple external hard drives and still have questions. Basically, I just need confirmation that what I'm about to do makes sense.

I just bought a Mercury Elite AL-Pro Firewire 800 Dual-Drive Raid from OWC and from what information I could find online, bought SD to do the actual back-up. The Mercury is connected directly to my intel imac (leopard not installed yet).

Last night I initialized the Mercury drive using SoftRaid's Mirror format.

My goal: I'd love to back-up my computer hd as well as 2 other external hard drives (both Lacie) to the Mercury (destination).

Do I partition the Mercury (destination) into 3 parts using Disk Utility first with the goal of using SD to back-up each source (main hd, 2 external drives) to a specific partition?

Then re-initialize the Mercury using SoftRaid?

Mirrors, Raids, partitions... all new to me and trying to wrap my head around it all...

Thank you!