ScalaIOExtrap: Elastic I/O Tracing and Extrapolation

Today’s rapid development of supercomputers has caused I/O performance to become a major performance bottleneck for many scientific applications. Trace analysis tools have thus become vital for diagnosing root causes of I/O problems. This work contributes an I/O tracing framework with (a) techniques to gather a set of lossless, elastic I/O trace files for small number of nodes, (b) a mathematical model to analyze trace data and extrapolate it to larger number of nodes, and (c) a replay engine for the extrapolated trace file to verify its accuracy. The traces can in principle be extrapolated even beyond the scale of presentday systems and provide a test if applications scale in terms of I/O. We conducted our experiments on three platforms: a commodity Linux cluster, an IBM BG/Q system, and a discrete event simulation of an IBM BG/P system. We investigate a combination of synthetic benchmarks on all platforms as well as a production scientific application on the BG/Q system. The extrapolated I/O trace replays closely resemble the I/O behavior of equivalent applications in all cases.