Calls for HDF5 metadata can result in many small reads and writes.
On metadata reads, collective metadata I/O can improve performance
by allowing the library to perform optimizations when reading the
metadata, by having one rank read the data and broadcasting it
to all other ranks.
Collective metadata I/O improves metadata write performance
through the construction of an MPI derived datatype
that is then written collectively in a single call.
This page lists the functions associated with HDF5 operations
that can issue metadata reads from the metadata cache,
but that currently provide no access property list parameter
by which to set a collective requirement individually
for those read operations.