different `io_type`: `netcdf,netcdf4` vs `pnetcdf,cdf5`

[guoqing-noaa]

I found there are different settings of the io_type in MPAS-Model streams.

Such as:
io_type="pnetcdf,cdf5"
or
io_type="netcdf,netcdf4"

I am curious what the differences are and what's the best settings in our practices

[clark-evans]

I found there are different settings of the io_type in MPAS-Model streams.

Such as: io_type="pnetcdf,cdf5" or io_type="netcdf,netcdf4"

I am curious what the differences are and what's the best settings in our practices

Based on the example for io_type at https://www2.mmm.ucar.edu/projects/mpas/site/documentation/users_guide/configuring_io.html#optional-stream-attributes, I believe that the second option is a modulator to the first; i.e., "pnetcdf,cdf5" means to use the CDF-5 codec when writing with pnetcdf. In your second example, I think "netcdf,netcdf4" would be equivalent to just "netcdf4," but there may be more nuance than I am aware of between netcdf4 as a modulator on netcdf and netcdf4 alone.

[guoqing-noaa]

@clark-evans Thanks for the information.
It looks like we should not have io_type="netcdf,netcdf4".

Do HFIP runs use netcdf4? Thanks!

[clark-evans]

@clark-evans Thanks for the information. It looks like we should not have io_type="netcdf,netcdf4".

Do HFIP runs use netcdf4? Thanks!

The HFIP runs used io_type = "pnetcdf,cdf5" from the outset without testing other options, though presumably io_type = "netcdf4" would also have worked per the guidance at https://www2.mmm.ucar.edu/projects/mpas/site/access_code/meshes.html#km-elliptical-refinement-mesh.