I recently bought a 40 Gb external h/d with a view to using it for my back-up medium. Since I only have a maximum of 10 Gb that I wish to back up, I partitioned the disk into volumes, designating one for back-up and the others for separate tasks.
When I went to run Retrospect there was a message that said Retrospect would require the entire disk - all other data would be erased. Surely such advanced software has a facility to back-up to a volume - much cheaper and less sophisticated programs do. Hopefully it's just my lack of familiarity with all the ins-and-outs of Retrospect, but I haven't been able to find a way round it yet. It'd be a pity, 'cause I upgraded to 6.0 not that long ago and haven't yet been able to use it.
Looking forward to hearing that I didn't blow my dough!