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Summary: Deconstructing Storage Arrays
Timothy E. Denehy, John Bent, Florentina I. Popovici,
Andrea C. Arpaci-Dusseau, and Remzi H. Arpaci-Dusseau
Department of Computer Sciences, University of Wisconsin, Madison
ABSTRACT
We introduce Shear, a user-level software tool that characterizes
RAID storage arrays. Shear employs a set of controlled algorithms
combined with statistical techniques to automatically determine the
important properties of a RAID system, including the number of
disks, chunk size, level of redundancy, and layout scheme. We illus-
trate the correctness of Shear by running it upon numerous simu-
lated configurations, and then verify its real-world applicability by
running Shear on both software-based and hardware-based RAID
systems. Finally, we demonstrate the utility of Shear through three
case studies. First, we show how Shear can be used in a storage
management environment to verify RAID construction and detect
failures. Second, we demonstrate how Shear can be used to extract
detailed characteristics about the individual disks within an array.
Third, we show how an operating system can use Shear to automat-
ically tune its storage subsystems to specific RAID configurations.
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