Scheduling Algorithms for Handling Updates in Shingled Magnetic Recording

Shingled recording has recently emerged as one promising candidate to sustain the historical growth of magnetic recording storage areal density. However, since the convenient update-in-place feature is no longer available in shingled recording, many sectors must be read and written back in order to update one sector. This leads to a significant update-induced latency overhead and makes conventional hard disk drive scheduling algorithms perform poorly. This paper concerns with the development of appropriate scheduling algorithms for shingled recording based hard disk drives. We first present a simple partial-update scheduling algorithm that can naturally embrace the update latency issue and achieves significant gains over conventional scheduling algorithms. We enhance this algorithm by incorporating a shortest update first policy, which can further reduce the update response time on an average by 70%. Finally, motivated by abundant workload spatial and temporal locality, we develop a spatio-temporal band coalescing scheme that can achieve an additional reduction of update response time of up to 96.8%.