Two-phase commit (2PC) has been widely used in distributed databases to ensure atomicity for distributed transactions. However, 2PC suffers from two limitations. First, 2PC incurs long latency as it requires two logging operations on the critical path. Second, when a coordinator fails, a participant may be blocked waiting for the coordinator's decision, leading to indefinitely long latency and low throughput.We make a key observation that modern cloud databases feature a storage disaggregation architecture, which allows a transaction's final decision to not rely on the central coordinator. We propose Cornus, a one-phase commit (1PC) protocol specifically designed for this architecture. Cornus can solve the two problems mentioned above by leveraging the fact that all compute nodes are able to access and modify the log data on any storage node. We present Cornus in detail, formally prove its correctness, develop certain optimization techniques, and evaluate against 2PC on YCSB and TPC-C workloads. The results show that Cornus can achieve 1.5× speedup in latency.

Two-phase commit (2PC) is widely used in distributed databases to ensure atomicity of distributed transactions. Conventional 2PC was originally designed for the shared-nothing architecture and has two limitations: long latency due to two eager log writes on the critical path, and blocking of progress when a coordinator fails. Modern cloud-native databases are moving to a storage disaggregation architecture where storage is a shared highly-available service. Our key observation is that disaggregated storage enables protocol innovations that can address both the long-latency and blocking problems. We develop Cornus, an optimized 2PC protocol to achieve this goal. The only extra functionality Cornus requires is an atomic compare-and-swap capability in the storage layer, which many existing storage services already support. We present Cornus in detail and show how it addresses the two limitations. We also deploy it on real storage services including Azure Blob Storage and Redis. Empirical evaluations show that Cornus can achieve up to 1.9X latency reduction over conventional 2PC.