How should I set up my external RAID?

So for Christmas I got one of the OWC Mercury Elite-Pro SATA RAID enclosures for use with my Alum iMac. I've bought two 500GB drives to put in it, but I'm torn on how to actually use the thing. I'll be getting into some heavier video editing later on in the year, but for now that kind of use is pretty light weight.

I could just stripe it and have a fast 1TB hanging off the iMac firewire, but then I was debating whether to actually just mount both drives separately and use one of them as a TimeMachine backup of my internal 500GB drive.

I don't really think I need to allot 500GB to backing up my internal drive, as the only things I really need to backup are my iTunes library and some documents, so I was thinking of just migrating my current USB external HDD to TimeMachine purposes (though would it have to be on constantly to use it with TimeMachine? I don't like to leave it on all the time), and not "wasting" 500GB on an unnecessary backup.

I also have the same rationale when thinking of setting up a mirrored RAID. It seems like a waste of space to mirror a 500GB drive just for backup purposes since this isn't a work machine and doesn't hold anything mission critical to my life most of the time.

I guess that does just leave striping the two into a single 1TB volume, though.

Anyway, I just wondered how other people would set this up? Thanks.

 

Yeah, part of the problem with me and my backing-up habits is that I've never had a drive fail on me. I still have an 20GB IBM drive from 1998 that's still going strong in a linux box with not even a peep, so my perception of drive reliability is a bit skewed.

I'll just play with it I suppose and see how it works. If I assume my RAID discs are more reliable than my internal iMac drive, if I were to stripe the RAID can you still partition the whole striped RAID into multiple volumes (so I could make one specifically for Time Machine) or can a striped disc only be seen as one volume?