3 ms·
I mistyped, I meant to say that a stalled sequencer stalls all schedulers. It's true that Corfu has impressive per-sequencer throughput (by moving most of the
by ngbronson 9y ago
I mistyped, I meant to say that a stalled sequencer stalls all schedulers. It's true that Corfu has impressive per-sequencer throughput (by moving most of the work onto other nodes), but you have to move to multiple sequencers to get to Spanner scale.
- CalvinDB 9y agoYes, you move to multiple sequencers, and you have them reach consensus via Paxos (to avoid problems from individual stalled sequencers).
- ngbronson 9y agoSo to get back to Spanner's availability (if you need it), you need the Calvin sequencer Paxos groups to span data centers. Since you're not exploiting the commutativity structure of transactions you need either a leader-based consensus implementation, which will have latency stalls when a leader becomes unavailable (amplified by the all-to-all communication), or you can use old-school 2 RTT Paxos, and your end latency ends up the same as Spanner. Lest it seem like I'm not actually a fan of the log-based approach, let me point out a way in which Calvin crushes Spanner: write contention. So long as the Calvin transactions can encode the application logic, they can support extremely high write rates on contended objects in the database. Spanner's 2PL, on the other hand, has single-object object update rates visible to the naked eye.