Alleviating Hot Data Write Back Effect for Shingled Magnetic Recording Storage Systems

Abstract

Shingled magnetic recording (SMR) is a novel technology that can significantly increase the disk capacity and reduce the cost. However, this new technology leads to write constraint that prohibits random writes to SMR disks. In order to solve this, current solutions utilize a persistent cache (PC) to change random writes to sequential ones. By doing this, nevertheless, the hot-data write-back effect will be triggered which inevitably incurs extra read-modify-write (RMW) operations. This paper presents a cache management scheme called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dual-buffer</i> to manage the overall SMR space, by which the PC is partitioned into the persistent buffer and the filter buffer. It leaves hot data in the filter buffer and moves cold data back to the SMR disk so that the hot data write-back effect can be alleviated. Since the PC may contain a large amount of valid data, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dual-buffer</i> also presents a prediction-based dynamic configuration strategy so hot data can be cached as much as possible. We conducted a series of experiments with synthetic traces. Experimental results show that our <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dual-buffer</i> scheme can shorten the average response time by 51.66% on average and reduce the total number of RMW operations by 98.76% on average compared to the previous work.