Deconstructing Storage Arrays
Timothy E. Denehy,
Florentina I. Popovici,
Andrea C. Arpaci-Dusseau,
Remzi H. Arpaci-Dusseau
Department of Computer Sciences
University of Wisconsin-Madison
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 illustrate the correctness of Shear by running it upon
numerous simulated 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
automatically tune its storage subsystems to specific RAID configurations.