I have a relatively large dataset (20GB) that I want to cache locally, but the machines it is running on only has about 8GB of RAM. Does mnesia in disc_copies mode support paging, or does the entire dataset have to fit in memory?
Mnesia disc_copies do get read entirely into memory. See http://erlang.org/faq/mnesia.html section 11.5. The files are also limited to 2GB unless you fragment the table.