Adaptive quorum designs reduce latency in wide area networks
Exploring Adaptive Byzantine Quorum Systems to Improve Latency in the WAN
Distributed, Parallel, and Cluster Computing
Summary
When computers spread across different locations need to agree on a decision, they use groups called quorums to vote securely. The size and members of these groups affect how fast decisions happen, especially over slow networks. The authors created a setup where different quorum designs can be tested fairly in the same system to see which makes things faster. They used simulations to find out how these designs change the waiting time for users.
What this means in practice
- •For distributed system engineers: Optimize quorum selection in BFT replication protocols to lower client latency across global data centers.
- •For cloud infrastructure teams: Improve the performance of fault-tolerant services by integrating adaptive quorum mechanisms in geographically distributed cloud environments.
Authors
Linus Gnan, Rüdiger Kapitza, Christian Berger
Abstract
Quorum systems enforce strict consistency in Byzantine fault-tolerant (BFT) state machine replication: Before a value is decided, a subset of replicas (called quorum) must exchange votes for the value. In wide-area networks, the size and composition of a quorum determines the speed at which replicas can make progress and thus impacts the latency perceived by clients. A variety of quorum constructions has been proposed, e.g., threshold, weighted, grid and others, but the literature offers little in the way of an apples-to-apples comparison. Each construction typically lives inside a different protocol implementation, so the influence of quorum design on client latency cannot be easily separated from other implementation effects, especially the use of optimization techniques. In this paper, we close that gap by extending BFT-SMaRt with a modular quorum-system abstraction that allows a variety of quorum constructions to live inside the same framework and interact with the same set of optimization techniques. Via our framework, we explore the impact of different quorum system constructions on client-observed latency in wide-area BFT replication using network simulation.