An update. I managed to get the I/O server running. It appears there is a conflict with Fortran unit numbers when running the I/O server with netCDF output enabled.
@cbengel provided a branch of rAM3 which used Fields Files outputs, which removed the conflict between Fortran unit numbers.
See here for further details: Issues with configuring the UM I/O server - #6 by Paul.Gregory
The default ROMIO_HINTS settings also provided a useful speedup.
I compiled a UM executable for the Sapphirerapids nodes on the normalsr queue, see : Building the UM to run on Gadi's Sapphire nodes - #4 by Paul.Gregory
That also provided a useful speedup, but I’m still a fair way behind AUS2200 in terms of kSU/day using the same domain decomposition. While the AUS2200 configuration is similar to rAM3, it’s not exact, so I want to run AUS2200 for a day or two and examine the I/O server logs to compare against the rAM3 setup.