snewman's comments have addressed most of this. (hey steve!) i'll just add that HRD has more predictable read and write latency, which most developers like a lo

snewman's comments have addressed most of this. (hey steve!) i'll just add that HRD has more predictable read and write latency, which most developers like a lot, but its writes are also slower on average, since they incur at least one Paxos round across datacenters.