Deconstructing Storage Arrays

Abstract

We present 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. We illustrate the correctness of Shear by running it upon numerous simulated configurations, and then verify its real-world applicability by applying Shear to both software-based and hardware-based RAID systems. Finally, we demonstrate the utility of Shear through two case studies. First, we show how Shear can be used in a storage management environment to verify RAID construction and detect failures. Second, we show how an operating system can use Shear to automatically tune its storage subsystems to specific RAID configurations.