IOPriority: To The Device and Beyond

In large scale data centers, controlling tail latencies of IO requests keeps storage performance bounded and predictable, which is critical for infrastructure resource planning. This work provides a transparent mechanism for applications to pass prioritized IO commands to storage devices. As a consequence, we observe much shorter tail latencies for prioritized IO while impacting nonprioritized IO in a reasonable manner. We also provide a detailed description of the changes we made to the Linux Kernel that enable applications to pass IO priorities to a storage device. Our results show that passing priorities to the storage device is capable of decreasing tail latencies by a factor of 10x while decreasing IOPS minimally.