BEGIN:VCALENDAR PRODID:-//Microsoft Corporation//Outlook MIMEDIR//EN VERSION:2.0 BEGIN:VEVENT DTSTART:20141118T200000Z DTEND:20141118T203000Z LOCATION:393-94-95 DESCRIPTION;ENCODING=QUOTED-PRINTABLE:ABSTRACT: The Lustre file system provides high aggregated I/O bandwidth and is in widespread use throughout the HPC community. Here we report on work (1) developing a model for understanding collective parallel MPI write operations on Lustre, and (2) producing a library that optimizes parallel write performance in a user-friendly way. We note that a system's default stripe count is rarely a good choice for parallel I/O, and that performance depends on a delicate balance between the number of stripes and the actual (not requested) number of collective writers. Unfortunate combinations of these parameters may degrade performance considerably. For the programmer, however, it's all about the stripe count: an informed choice of this single parameter allows MPI to assign writers in a way that achieves near-optimal performance. We offer recommendations for those who wish to tune performance manually and describe the easy-to-use T3PIO library that manages the tuning automatically. SUMMARY:A User-Friendly Approach for Tuning Parallel File Operations PRIORITY:3 END:VEVENT END:VCALENDAR