Multithreaded Two-Phase I/O: Improving Collective MPI-IO Performance on a Lustre File System

ROMIO, a representative MPI-IO implementation, has been widely used in recent large-scale parallel computations. The two-phase I/O optimization scheme of ROMIO improves I/O performance for non-contiguous access patterns, however, this scheme still has room to improve performance to make it suitable for recent data-intensive computing. We propose overlapping data exchange operations with file I/O operations by using a multithreaded scheme to achieve further I/O throughput improvement. We show up to 60% improvement by the multithreaded two-phase I/O relative to the original two-phase I/O in performance evaluation of collective write operations on a Lustre file system of a Linux PC cluster.