Key-value stores (KVStores), such as LevelDB and Redis, have been widely used in real-world production environments. To guarantee data durability and availability, traditional KVStores suffer from high write latency, mainly caused by the long network and data-persisting time. To solve this problem, this article presents a novel data-persisting path for KVStores, allowing remote clients to persist data to the KVStore server with mu s -level latency. The novelty of this study is threefold. First, we propose PMRDirect, which utilizes a persistent memory region (PMR) in the NVM express standard to construct a direct data-persisting path from the RDMA networking card (NIC) to the PMR region inside an SSD. Second, to showcase PMRDirect in KVStores, we developed a new accessing stack called PMRAccess, enabling remote clients to access existing KVStores and providing durability for each write request. Specifically, we present a low-latency RDMA-based messaging mode and a chunk-based PMR management in PMRAccess to reduce write latency and improve system throughput. Finally, we conducted extensive experiments to evaluate the performance of our proposals. We first compared PMRDirect with a few remote data-persisting paths to show its effectiveness. Then, we evaluated PMRAccess upon two KVStores, including LibCuckoo (an in-memory KVStore) and LevelDB (an in-storage KVStore). The results showed that PMRAccess outperformed the SSD-based accessing stack by up to 6.1x in write throughput and 36x in write tail latency, and it achieved 1.7x higher write throughput and 0.59x lower write tail latency over the PMEM-based accessing stack. Further, we conducted a system-to-system comparison between the PMRAccess-integrated LibCuckoo and Redis, and the results showed our proposal achieved up to 13x higher throughputs and 40x lower write latency than Redis.
