SWARM: Replicating Shared Disaggregated-Memory Data in No Time

TL;DR

SWARM introduces a novel replication scheme for disaggregated memory that achieves single-roundtrip operations, strong consistency, and wait-freedom, significantly improving latency and availability in shared-memory data centers.

Contribution

It presents SWARM, the first wait-free, strongly consistent replication protocol for disaggregated memory, with innovative techniques Safe-Guess and In-n-Out.

Findings

SWARM-KV has marginal latency overhead compared to unreplicated store.

SWARM-KV offers lower latency and better availability than FUSEE.

SWARM achieves single-roundtrip read/write operations with strong consistency.

Abstract

Memory disaggregation is an emerging data center architecture that improves resource utilization and scalability. Replication is key to ensure the fault tolerance of applications, but replicating shared data in disaggregated memory is hard. We propose SWARM (Swift WAit-free Replication in disaggregated Memory), the first replication scheme for in-disaggregated-memory shared objects to provide (1) single-roundtrip reads and writes in the common case, (2) strong consistency (linearizability), and (3) strong liveness (wait-freedom). SWARM makes two independent contributions. The first is Safe-Guess, a novel wait-free replication protocol with single-roundtrip operations. The second is In-n-Out, a novel technique to provide conditional atomic update and atomic retrieval of large buffers in disaggregated memory in one roundtrip. Using SWARM, we build SWARM-KV, a low-latency, strongly consistent and highly available disaggregated key-value store. We evaluate SWARM-KV and find that it has marginal latency overhead compared to an unreplicated key-value store, and that it offers much lower latency and better availability than FUSEE, a state-of-the-art replicated disaggregated key-value store.