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International Journal of Stochastic Analysis
Volume 2011 (2011), Article ID 390548, 21 pages
http://dx.doi.org/10.1155/2011/390548
Research Article

A Stochastic Analysis of Hard Disk Drives

School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15217, USA

Received 16 November 2010; Revised 10 February 2011; Accepted 15 February 2011

Academic Editor: Karl Sigman

Copyright © 2011 Field Cady et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We provide a stochastic analysis of hard disk performance, including a closed form solution for the average access time of a memory request. The model we use covers a wide range of types and applications of disks, and in particular it captures modern innovations like zone bit recording. The derivation is based on an analytical technique we call “shuffling”, which greatly simplifies the analysis relative to previous work and provides a simple, easy-to-use formula for the average access time. Our analysis can predict performance of single disks for a wide range of disk types and workloads. Furthermore, it can predict the performance benefits of several optimizations, including short stroking and mirroring, which are common in disk arrays.