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> Before we get started, allow me to suggest the following: Ignore the CAP theorem in the context of this discussion. Just forget about it. It’s not relevant fo
by rdtsc 10y ago
> Before we get started, allow me to suggest the following: Ignore the CAP theorem in the context of this discussion. Just forget about it. It’s not relevant for the type of modern architectural deployments discussed in this post where network partitions are rare.
Anyone worried about that statement. Ok so they are rare, but what happens when they do occur? File corruption is rare as well but in our large deployment over thousands of servers I see it happen pretty often.
- freels 10y agoCalvin is still a CP system, so nodes outside of the quorum cannot proceed. The point however is that partitions are rare enough that a CP system can still provide a high level of availability, despite the theoretical limitation. Eric Brewer, who came up with the CAP theorem explicitly makes this point here: https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/45855.pdf https://static.googleusercontent.com/media/research.google.c...
- rdtsc 10y agoThat's an excellent description. And post's author describes that systems behave like CP. But in general, Google's network is very different than other networks. With their resources they can provide guarantees and capacities other run-of-the-mill data centers can't. So others probably shouldn't listen and assume it applies to them as well.
- freels 10y agoIME, while Google's network is really good (based on my experience w/ GCP at least), AWS cross-region traffic, for example, is still pretty reliable. Reliable enough, at least, that trading off perfect resiliency in the face of partitions is worth it to gain strong consistency semantics. IMO behavior in the face of partitions is a bit of a red herring. The latency tradeoffs required in a geo-replicated CP vs AP system is much more relevant.