FairCS: A Fairness-aware Cleaning Slowdown on an SMR Disk

Nowadays, shingled magnetic recording (SMR) disks have emerged as an alternative option to conventional hard disk drives (HDDs) owing to their high storage density and cost-effectiveness. However, when multiple users compete for access to an SMR disk simultaneously, certain users may experience significant slowdowns, leading to unfairness due to the inherent characteristics of SMR disks. Specifically, as the available space on an SMR disk dwindles, some users may be required to wait while the disk performs a time-consuming clean operation (i.e., cleaning slowdown) to reclaim sufficient space. To provide fair management mechanisms in SMR storage stacks, we propose FairCS (Fairness-aware Cleaning Slowdown) that is a host-software solution designed to promote fairness among concurrent users accessing an SMR disk. Our method aims to enhance users’ awareness of fairness by mitigating the impact of cleaning slowdowns on an SMR disk. Experimental results demonstrate that FairCS not only narrows the gap of minimum and maximum cleaning slowdowns, but also reduces long-tail latency, thereby enhancing overall system fairness.