- If you use the Parallel HDF5 library, open a communicator for each node and add just one process to that communicator.
- You may also try to use the sequential library, but then you have to make sure that only a particular process creates/modifies/closes the file that is written to. This approach has not been tested.
Pros: should be faster than 1)
Cons: multiple files to handle, not tested
Also there can be other approaches if you decide to go with multiple files. For example, each process writes a flat binary file and one can use the HDF5 external datasets storage feature to create a wrapper HDF5 file to combine all data. See the section on Dataset Creation Property Lists under Property Lists in the HDF5 Tutorial.