Forthcoming update to the format of netCDF files produced by the conversion of GRIB data on the CDS

This is my first post to the forum, so my apologies if I am asking in the wrong place.

I have many years of old data in the previous netCDF file format (netCDF 3, 64-bit offset). I have downloaded some data in the new netCDF format (netCDF-4), but reading from the new files is approximately 3 orders of magnitude slower than the old files (5.099 s vs. 0.0084 s).

They both appear to be valid netCDF files and the data looks normal. My only guess is that perhaps the chunk size for the netCDF-4 files is particularly inefficient? I can provide more details if it would be of any help.

Thanks, Ken Bowman