Google would need more than one raw GB per GB, because there is some risk the drive would fail. I don't know what the answer would be, my NAS is a two bay solut

Google would need more than one raw GB per GB, because there is some risk the drive would fail. I don't know what the answer would be, my NAS is a two bay solution, so I waste 50% of the capacity, a 4 bay one might only waste 25%. And that is without accounting for disk replacement cost, operating and electrictal costs and so on.