Section: New Results

Scheduling the I/O of HPC Applications Under Congestion

Participants : Ana Gainaru [University of Illinois at Urbana Champaign] , Guillaume Aupy, Anne Benoit, Franck Cappello, Yves Robert.

A significant percentage of the computing capacity of large-scale platforms is wasted due to interferences incurred by multiple applications that access a shared parallel file system concurrently. One solution to handling I/O bursts in large-scale HPC systems is to absorb them at an intermediate storage layer consisting of burst buffers. However, our analysis of the Argonne's Mira system shows that burst buffers cannot prevent congestion at all times. As a consequence, I/O performance is dramatically degraded, showing in some cases a decrease in I/O throughput of 67%.

In this work, we analyze the effects of interference on application I/O bandwidth, and propose several scheduling techniques to mitigate congestion. We focus on typical HPC applications, which have a periodic pattern consisting of some amount of computation followed by some volume of I/O to be transferred. We show through extensive experiments that our global I/O scheduler is able to reduce the effects of congestion, even on systems where burst buffers are used, and can increase the overall system throughput up to 56%. We also show that it outperforms current Mira I/O schedulers, even for non-periodic applications.

This work has been published in IPDPS'15 [26] .