Optimizing Performance for Open-Channel SSDs in Cloud Storage System

Abstract

In large-scale cloud storage systems, Solid-State Drive (SSD) has been broadly used as the mainstream storage device because it has the advantages of low access latency and high throughput. However, conventional SSD is a black-box system to host softwares, thus failing to fully exploit the benefits of NAND flash and provide high quality of service (QoS). On the other hand, Open-Channel SSD (OCSSD) which exposes its internal information to the host software, has the potential to solve this problem. However, existing OCSSD fails to achieve anticipated performance under heavy workloads. To this end, we propose an advanced OCSSD-based driver developed with the novel data placement policy, redefined garbage collection (GC) with copyback technique, efficient prefetch read scheme, and fast live upgrade method. Our work describes the consistent efforts to pursue high performance and QoS in OCSSDs with different approaches. The evaluation results show that our novel Open-Channel SSD is able to provide high I/O throughputs and predictable I/O latencies. For example, our Open-Channel SSD can improve I/O throughputs by 103% and reduce the 99th percentile latency by 62.9% on average compared with the state-of-the-art NVMe SSDs.