[dnanian]

I'm sorry, I'm still confused. What is the 160GB drive? I thought it was a backup. Is this an internal drive?

Is your 500GB completely full, and you're planning on moving that data to the Drobo? Or are you trying to back up the data on the 500GB to the Drobo?

How many partitions do you have on the source -- in other words, how many 'volumes' are you actually trying to back up here?