Simulation for a Shingled Magnetic Recording Disk

Abstract

Shingled magnetic recording (SMR) is a new technology based on partially overlapping, or shingling, adjacent tracks, which is capable of increasing the density of a disk drive up to 10 Tbit/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . To write data on overlapping tracks may erase data being written previously. Therefore, without any data translation layer to redirect updates to different locations to avoid unintended data erasures, the SMR disk cannot be used as a conventional disk to perform unrestricted reads/writes directly. Various data translation/mapping strategies have been proposed to allow the disk to perform unrestricted reads/writes. However, these strategies have tradeoffs in terms of system performance and cost, such as disk space utilization. Nevertheless, system performance varies for different applications and under different workload conditions. To help optimize the design of a data translation layer for a SMR disk, simulation software is required to analyze tradeoffs and to fine tune parameters for data translation/remapping strategies. We have designed and developed a simulation software for SMR disks. This software can analyze both system performance and disk space utilization. The SMR disk simulation uses the shingled disk profiles generated from the conventional disk profiles which have been experimentally validated. Evaluation studies show that the simulation software can accurately simulate SMR disk performance. This software will be a useful platform to design and test the shingle translation layer (STL) for a SMR disk with different disk layouts and data management strategies and garbage collection algorithms.