Hydis: A Hybrid Consistent KVS with Effective Sync Among Replicas

Distributed storage systems distribute user loads across regions. User requests from different geographical locations are directed to the nearest data center, benefiting reduced service latency and improved service quality. However, the consistency among regions holds against availability and richness of the underlying data services. To address these constraints, our study proposes Hydis, a hybrid consistency distributed key-value storage system based on optimized replica synchronization. Hydis guarantees high availability and scalability for geographically distributed systems and uses Conflict-free Replicated Data Types to construct HybridLattice that supports various consistency models. A novel Writeless-Consistency strategy is proposed to improve the synchronization efficiency between replicas, and a dynamic synchronization optimization based on this strategy is implemented for consistency algorithm to effectively reduce the synchronization overhead of distributed storage systems. A performance evaluation of the Hydis cluster deployed on Alibaba Cloud showed that the strong consistency algorithm in Hydis outperformed the Raft algorithm by 1.8X. Additionally, the causal consistency algorithm in Hydis outperformed the traditional Vector Clock algorithm by 2.5X.