Hi Jim,The goal of ParaView Catalyst is to enable post-processing on the compute nodes. This contrasts with the traditional post-processing workflow: save derived data, move the data on a different machine, create visualizations with it. For this we link a slimmed down version of ParaView to the simulation code, pass the data on each compute node to the ParaView running on that node and perform post-processing using any VTK/ParaView pipeline. The pipeline is written in Python. We can save processed datasets, visualizations or we can send processed data to a remote ParaView.The challenge for cam5 (fv, cam5, trop_mam3) is that computational load balance (chunking) that is performed by the physics module seems to imply spatial non-coherence between data stored on different compute nodes. (columns are not next to each other on one compute node).Our current project is limited in goals (and funds) so I will not pursue the PIO route further at the moment.Just out of curiosity though, why do you want to build larger blocks on the compute nodes? This will help us for visualization, but the physics module does not seem to need that.Thank you,