ASCAR: Automating Contention Management for High-Performance Storage Systems

Abstract

High-performance parallel storage systems, such as those used by supercomputers and data centers, can suffer from performance degradation when a large number of clients are contending for limited resources, like bandwidth. These contentions lower the efficiency of the system and cause unwanted speed variances. ASCAR (Automatic Storage Contention Alleviation and Reduction) is a storage traffic management system for improving the bandwidth utilization and fairness of resource allocation. ASCAR regulates I/O traffic from the clients using a rule-based algorithm that controls the congestion window and rate limit. The rule-based client controllers are fast responding to burst I/O because no runtime coordination between clients or with a central coordinator is needed; they are also autonomous so the system has no scale-out bottleneck. Evaluation shows that the ASCAR prototype can improve the throughput of all tested workloads - some by as much as 35%.