Cloud local disks are attractive for their affordable price and high performance. The recent advancement in CPUs motivates cloud vendors to further multiplex the computing resources to serve more users. Unfortunately, such proposals are constrained by the limited offerings of cloud local disks per server as the underlying storage devices are either large but slow (e.g., HDDs) or fast yet small (e.g., NVMe SSDs).
In this paper, we explore the possibility of leveraging high-capacity QLC-based SSDs for cloud local disks. However, the three preliminary unsuccessful attempts indicate that QLC SSDs cannot simply work as drop-in replacement. The root cause is the two levels of write amplification (WA) caused by device-level address mapping with Indirection Unit and NAND-level garbage collection.
With these lessons learned, we propose SONIC, the next-gen local disks in the OASIS cloud. SONIC includes a high-performance SSD as write buffers and a large-capacity QLC SSD for persistence. With a two-level Logical to Physical (L2P) address mapping table, SONIC achieves fine-grained (4KB) data accessing and significantly alleviates the two levels of WA. Results show that SONIC always prevails with superior performance and can achieve up to 2.47x, 1.82x, and 2.03x speedups against the second-best peers in micro, application and deployment benchmarking, respectively. As of now, we have deployed SONIC on thousands of servers and made SONIC open-source to the public.