3 ms·
It is, in fact, not the same for every DB. Databases vary significantly in their default and maximum guarantees for successfully acknowledged writes; Mongo choo
by aphyr 8y ago
It is, in fact, not the same for every DB. Databases vary significantly in their default and maximum guarantees for successfully acknowledged writes; Mongo chooses fairly weak ones. By contrast, consider systems like VoltDB, which aims for strict serializability by default, or etcd, which offers linearizability/sequential reads by default.
- nvarsj 8y ago> etcd, which offers linearizability/sequential reads by default Not quite true - you have to opt-in to quorum reads in etcd. Otherwise it just returns the first read (which used to be the default in k8s and caused a lot of grief).
- aphyr 8y agoAh, yes, sorry! I forgot exactly how that all shook out. I thiiink that prevents dirty reads, and with client monotonicity you can recover sequential consistency? Not sure how many clients actually do that; maybe they just do regular reads at RC...
- ideal0227 8y agoThat is true. etcd v3 provides l-read by default. You have to opt-out that to improve latency.
- ideal0227 8y agoNo. You are wrong. etcdv3 enables l-read by default.