The following figure shows the typical I/O software stack that is needed to make optimum use of the storage hardware in an HPC system. The role of the High Level I/O Library is often crucial. First, it conveniently maps application abstractions to a structured, portable file format. Second, when the library is a parallel I/O library, it can achieve superior I/O rates by going through the MPI-IO interface to access an underlying parallel file system like Lustre, as described in the Parallel I/O roadmap.

The present roadmap includes topics about two major high-level libraries: PnetCDF, a parallel implementation of the netCDF API and the related file format; and PHDF5, a parallel library for working with HDF5 formatted files. ADIOS is also touched upon briefly.