Idler : I/O Workload Controlling for Better Responsiveness on Host-Aware Shingled Magnetic Recording Drives

Abstract

Host-Aware/Drive-Managed Shingled Magnetic Recording (SMR) drives can accept non-sequential writes using a buffer called media cache. Data in the media cache will be migrated to its designated location by a cleaning process if the buffer is full (blocking cleaning) or the drive is idle (idle cleaning). However, blocking cleanings can severely extend the I/O response time. Therefore, it is crucial to fully understand the cleaning process and find ways of mitigating the caused performance degradation. In this article we further evaluate the cleaning process and propose a potential remedy scheme called Idler on Host-Aware SMR drives. Idler adaptively induces idle cleanings based on dynamic workload characteristics and media cache usages to reduce the severity of blocking cleanings. Our evaluations show that in the workloads with a small non-sequential write ratio (about 10 percent), Idler can reduce the tail response time and the workload finish time by 56-88 and 10-23 percent, respectively, compared with those without such control. With the help of an external write buffer on an SSD, the tail response time of SMR drives with Idler can be closer to that of conventional disk drives.