AFAIK

you can raid two different size and make of hdd

it is just that:

1. for raid-0 (striping) the total is the lowest size times 2. eg: 200gb + 320gb = 400gb, (the 320 will only utilize 200gb only). this is also same with raid-1, except raid-1 is mirroring, so the total for the above drives is 200gb only(as the lowest is 200gb, so the 320 will use up to 200gb to mirror a.k.a copy exactly what the initial 200gb has.

2. it is said by some one here in LYN, that using different size and make will tax your raid chip, since different make have different specifications.

@ ~hunter~
what are you trying to say?
i failed to comprehend you problem