Optimizing I/O for Petascale Seismic Simulations on Unstructured Meshes

SeisSol simulates earthquake dynamics by coupling seismic wave propagation and dynamic rupture simulations with high order accuracy on fully adaptive, unstructured meshes. In this paper we present an optimization of SeisSol´s I/O implementations to establish a workflow that supports petascale simulations on large unstructured datasets. Our implementations can handle meshes with more than 1 billion cells and 660 billion degrees of reedom. The results show that SeisSol can initialize the mesh structure within 35 seconds on 2048 SuperMUC nodes from our new optimized mesh format. For the wave field output we implemented carefully tuned I/O routines based on HDF5 and MPI-IO. With an aggregation strategy we are able to increase the write bandwidth from 832 MiB/s to 6.7 GiB/s on 2048 SuperMUC nodes.