Consistency or latency? A quantitative analysis of replication systems based on replicated state machines

Existing theories like CAP and PACELC have claimed that there are tradeoffs between some pairs of performance measures in distributed replication systems, such as consistency and latency. However, current systems take a very vague view on how to balance those tradeoffs, e.g. eventual consistency. In this work, we are concerned with providing a quantitative analysis on consistency and latency for widely-used replicated state machines(RSMs). Based on our presented generic RSM model called RSM-d, probabilistic models are built to quantify consistency and latency. We show that both are affected by d, which is the number of ACKs received by the coordinator before committing a write request. And we further define a payoff model through combining the consistency and latency models. Finally, with Monte Carlo based simulation, we validate our presented models and show the effectiveness of our solutions in terms of how to obtain an optimal tradeoff between consistency and latency.