Do we still need IO schedulers for low-latency disks?
C.M. Whitaker, Sidharth Sundar, Bryan Harris, Nihat Altiparmak
Abstract
The performance of recent data storage devices has significantly improved over previous generations, with lower latency, greater throughput, and greater parallelism. Since we now have Ultra-Low Latency (ULL) data storage devices capable of providing data in less than 10 microseconds, in this paper we question the need for IO schedulers for better performance and energy efficiency. Specifically, we measure the latency costs of Linux IO scheduling algorithms and investigate their impact on overall performance and energy efficiency using a ULL storage device, a power meter, and various IO workloads. Our observations indicate that IO schedulers for ULL storage either do not help or significantly increase request latencies while also negatively impacting throughput and energy efficiency. Although we recognize the value of IO schedulers for slower devices or for other metrics such as fairness and QoS, we believe that IO schedulers have become unnecessary for ULL devices to improve performance or energy efficiency.