Out-of-core MUMPS

Hi,

I have a question related to the "out-of-core" option. Suppose I have 32GB of RAM available, which is the best approach to use to solve a strongly coupled problem with around 2 millions DoF? 1) give a lot of in-core memory (like 15-20 GB) or 2) give a small amount of in-core memory (around 5GB) and leave the remaining for the computation?

Any idea is more than welcome,

Best,
J