Tornado Codes for MAID Archival Storage

Abstract

This paper examines the application of Tornado codes, a class of low density parity check (LDPC) erasure codes, to archival storage systems based on massive arrays of idle disks (MAID). We present a log- structured extent-based archival file system based on Tornado Coded stripe storage. The file system is combined with a MAID simulator to emulate the behavior of a large-scale storage system with the goal of employing Tornado Codes to provide fault tolerance and performance in a power-constrained environment. The effect of power conservation constraints on system throughput is examined, and a policy of placing multiple data nodes on a single device is shown to increase read throughput at the cost of a measurable, but negligible, decrease in fault tolerance. Finally, a system prototype is implemented on a 100 TB Lustre storage cluster, providing GridFTP accessible storage with higher reliability and availability than the underlying storage architecture.