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I would argue that by the time you've chosen Paxos or some other majority quorum commit protocol, you're already well aware that you're building a CP system, an

I would argue that by the time you've chosen Paxos or some other majority quorum commit protocol, you're already well aware that you're building a CP system, and that availability and latency aren't your main concern. A majority quorum is basically the most obvious (and somewhat brute force) way of providing serializable consistency in the system. The one non-majority quorum commit protocol that most people are probably already familiar with is the "sloppy quorum" replication in Dynamo systems[1] (e.g. Cassandra, Riak, Voldemort, etc.). Basically, since the quorum is configurable on a per-cluster basis instead of being inherent to the protocol, and usually isn't a majority of the cluster, the system can still make progress when half of the nodes are unreachable. (But of course, as the paper notes, this means that you need to resolve conflicts some other way, which adds a whole bunch of complexity.) 1: http://www.allthingsdistributed.com/files/amazon-dynamo-sosp2007.pdf http://www.allthingsdistributed.com/files/amazon-dynamo-sosp...

dllthomas 10y ago
> you're already well aware that you're building a CP system, and that availability and latency aren't your main concern Assuming you've chosen correctly between CP and AP approaches, this tells us that availability and latency aren't as important as consistency. But there's nothing that says they aren't arbitrarily close...
- elvinyung 10y ago
  Yeah, definitely -- I agree that the decision doesn't mean to just to blindly throw away availability optimizations once you've decided that consistency is important. Actually, invoking CAP probably didn't add to my message. What I meant to say is that people don't talk about non-majority quorum commits that much because the interesting part is that the serializability comes with majority/overlapping quorums.
  - dllthomas 10y ago
    As I read it, the comment you were replying to was still restricting its discussion to overlapping quorums, and merely pointing out that that's not actually synonymous with majority.
    - elvinyung 10y ago
      Fair enough :) I guess my mind latched onto the "it still seems under-explored" part and wanted to try and respond to that.

dllthomas 10y ago

> you're already well aware that you're building a CP system, and that availability and latency aren't your main concern Assuming you've chosen correctly between CP and AP approaches, this tells us that availability and latency aren't as important as consistency. But there's nothing that says they aren't arbitrarily close...

elvinyung 10y ago
Yeah, definitely -- I agree that the decision doesn't mean to just to blindly throw away availability optimizations once you've decided that consistency is important. Actually, invoking CAP probably didn't add to my message. What I meant to say is that people don't talk about non-majority quorum commits that much because the interesting part is that the serializability comes with majority/overlapping quorums.
- dllthomas 10y ago
  As I read it, the comment you were replying to was still restricting its discussion to overlapping quorums, and merely pointing out that that's not actually synonymous with majority.
  - elvinyung 10y ago
    Fair enough :) I guess my mind latched onto the "it still seems under-explored" part and wanted to try and respond to that.