Hierarchical Data Format version 5 (HDF5) is a set of file formats, libraries, and tools for storing and managing large scientific datasets. Originally developed at the National Center for Supercomputing Applications, it is currently supported by the non-profit HDF Group.
HDF5 is different product from previous versions of software named HDF, representing a complete redesign of the format and library. It also includes improved support for parallel I/O. The HDF5 file format is not compatible with HDF 4.x versions. You can use the 'h5toh4' and 'h4toh5' converters that are available on all NERSC machines.