Relation between Paxos and Snapshot Isolation for concurrency control

Question

I was wondering what is the actual relationship between Paxos based replication schemes and different concurrency models like snapshot isolations. Could anybody kindly able to explain these two in regards to their relationship and with few practical examples?

Answer 1

Snapshot isolation is a strong consistency concurrency criterion in the sense that it totally orders conflicting updates. Total order is equivalent to consensus in distributed systems. Paxos is a solution for consensus in distributed systems with process faults. So the answer to your question is: The relationship between snapshot isolation and Paxos-based replication schemes is that they should be equally hard to implement in a theoretical sense (i.e., will be possible with the same assumptions).

Other examples of strong consistent concurrency criteria are serializability, linearizability, and sequential consistency. In contrast, weak consistent criteria such as causal consistency or eventual consistency don't need consensus and are thus fundamentally different from the Paxos-based replication schemes that you might have seen.