Ripping = Reading
There seem to a number of BD drives that don't play 100% nice on the Mac Pro. I have an LG drive (
http://www.newegg.com/Product/Product.aspx?Item=N82E16827136183) and, while ripping perfectly, the drive seeks with a noticeable "click click" every 15 seconds or so if there isn't a disk in it. I recall reading other reports from Mac Pro uses who had identical issues with other brands/models of drives. Make sure the drive you choose doesn't exhibit this behavior.