The TickerTAIP parallel RAID architecture

Abstract

Traditional disk arrays have a centralized architecture, with a single controller through which all requests flow. Such a controller is a single point of failure, and its performance limits the maximum number of disks to which the array can scale. We describe TickerTAIP, a parallel architecture for disk arrays that distributes the controller functions across several loosely coupled processors. The result is better scalability, fault tolerance, and flexibility. This article presents the TickerTAIP architecture and an evaluation of its behavior. We demonstrate the feasibility by a working example, describe a family of distributed algorithms for calculating RAID parity, discuss techniques for establishing request atomicity, sequencing, and recovery, and evaluate the performance of the TickerTAIP design in both absolute terms and by comparison to a centralized RAID implementation. We also analyze the effects of including disk-level request-scheduling algorithms inside the array. We conclude that the Ticker TAIP architectural approach is feasible, useful, and effective.