An Efficient and Flexible Parallel I/O implementation for the CFD General Notation System

One important, often overlooked, issue for large, three dimensional time-dependent computational fluid dynamics (CFD) simulations is the input and output performance of the CFD solver, especially for large time-dependent simulations. The development of the CFD General Notation System (CGNS) has brought a standardized and robust data format to the CFD community, enabling the exchange of information between the various stages of numerical simulations. Application of this standard data format to large parallel simulations is hindered by the reliance of most applications on the CGNS Mid-Level Library. This library has only supported serialized I/O. By moving to HDF5 as the recommended low level data storage format, the CGNS standards committee has created the opportunity to support parallel I/O. In our work, we present the parallel implementation of the CGNS Mid-Level Library and an I/O request-queuing approach to overcome some limitations of HDF5. We also present detailed benchmarks on a parallel file system for typical structured and unstructured CFD application I/O patterns.