From Flash to 3D XPoint: Performance Bottlenecks and Potentials in RocksDB with Storage Evolution

Storage technologies have undergone continuous innovations in the past decade. The latest technical advancement in this domain is 3D XPoint memory. As a type of Non-volatile Memory (NVM), 3D XPoint memory promises great improvement in performance, density, and endurance over NAND flash memory. Compared to flash based SSDs, 3D XPoint based SSDs, such as Intel's Optane SSD, can deliver unprecedented low latency and high throughput. These properties are particularly appealing to I/O intensive applications. Key-value store is such an important application in data center systems. This paper presents the first, in-depth performance study on the impact of the aforesaid storage hardware evolution to RocksDB, a highly popular key-value store based on Log-structured Merge tree (LSM-tree). We have conducted extensive experiments for quantitative measurements on three types of SSD devices. Besides confirming the performance gain of RocksDB on 3D XPoint SSD, our study also reveals several unexpected bottlenecks in the current key-value store design, which hinder us from fully exploiting the great performance potential of the new storage hardware. Based on our findings, we also present three exemplary case studies to showcase the efficacy of removing these bottlenecks with simple methods, achieving a performance improvement by up to 18.8%. We further discuss the implications of our findings for system designers and users to develop schemes in future optimizations. Our study shows that many of the current LSM-tree based key-value store designs need to be carefully revisited to effectively incorporate the new-generation hardware for realizing high-speed data processing.