The main RAID configurations are as follows:
RAID0: This basically takes every single drive in the configuration, and turns it into one super fast super big drive.
Pros: Fast, fast fast fast
Cons: You've got twice as much chance of your drive exploding and losing everything
RAID1: 'mirror', both drives will be an exact, 1 for 0 copy of each other. This is not a backup, it's redundancy. It's a failsafe, so if one drive dies, the other will have the same stuff on it (but if you delete a file, both drives delete that file)
Pro: If one drive dies, just run everything offf the other, no need to re-install operating systems, configurations, etc etc etc.
Con: (at least) Twice as expensive, and as said before if you empty the trash without checking properly and you lose something you need, it's a total bitch to get it back.
RAID5: I'm a little hazy on this, but you have upwards of three drives, and somehow it magically writes data across all of these. The fancy thing here is that if one of the drives in the array kicks the bucket, there will be enough 'leftover' data on the other two to, reconstruct the dead drive one you plug a replacement in. I'm pretty sure this is what DROBO does, and seems pretty ideal.
RAID6, 10, etc etc: I have no idea what these even are.
If it were me, I'd grab a RAID0 with two 10,000rpm 500GB (or smaller, maybe) drives to edit from, then have a RAID1 with two 2tb 'green' drives (low power, quiet, apparently lots of people use these for backing up servers and such???) which will hold literally
every bit of raw footage you ever record.
Though if money were no object, a DROBO and a massive SSD to edit off.... mmmmm...
Keeping data safe is pretty important, at minimum I'd keep a drive for footage, and have that backed up somewhere else as well.