iTunes and iPhotos need expansion

[RikPierce]

My internal drives are way crowded. My expectation is to move both iTunes and iPhoto to their own external drives. I have 6 hard drives chained to each other and I'd like to devote a terabyte to iTunes (I have a lot of video) a 500 gig to my iPhotos. So I would like SuperDuper to back these drives up to two other drives as well as backing up my internal drives. At the moment I believe I am backed up on a 500 gig drive that is bootable which I'm hoping to be able to continue so that if my internal fails, I'll be able to boot from the external. That's right, isn't it?

Is there anything I need to be careful about? Should this be straightforward?