Cache Partition Management for Improving Fairness and I/O Responsiveness in NVMe SSDs

NVMe SSDs have become mainstream storage devices thanks to their compact size and ultra-low latency. It has been observed that the impact of interference among all concurrently running streams (i.e., I/O workloads) on their overall responsiveness differs significantly, thus leading to unfairness. The intensity and access locality of streams are the primary factors contributing to interference. A small-sized data cache is commonly equipped in the front-end of SSDs to improve I/O performance and extend the device's lifetime. The degree of parallelism at this level, however, is limited compared to that of the SSD back end, which consists of multiple channels, chips, and planes. Therefore, the impact of interference can be more significant at the data cache level. In this paper, we propose a cache division management scheme that not only contributes to fairness but also boosts I/O responsiveness across all workloads in NVMe SSDs. Specifically, our proposal supports long-term data cache partitioning and short-term cache adjustment with global sharing, ensuring better fairness and further enhancing cache utilization efficiency in multi-stream scenarios. Trace-driven simulation experiments show that our proposal improves fairness by an average of 66.0% and reduces overall I/O response time by between 3.8% and 18.0%, compared to existing cache management schemes for NVMe SSDs.