Light-weight parallel I/O analysis at scale

Input/output (I/O) operations can represent a significant proportion of the run-time when large scientific applications are run in parallel. Although there have been advances in the form of file-format libraries, file system design and I/O hardware, a growing divergence exists between the performance of parallel file systems and compute processing rates. In this paper we utilise RIOT, an input/output tracing toolkit being developed at the University of Warwick, to assess the performance of three standard industry I/O benchmarks and mini-applications. We present a case study demonstrating the tracing and analysis capabilities of RIOT at scale, using MPI-IO, Parallel HDF-5 and MPI-IO augmented with the Parallel Log-structured File System (PLFS) middle-ware being developed by the Los Alamos National Laboratory.