I added a reference to this thread in the comments on the documentation at
/doc/openacs-4/acs-admin.html
I don't have time to do the research and draft a skeleton of what the backup chapter/ section might contain, but anyone else with a few free moments could draft something and post it in the comments to the documentation. Remember - the comment functionality allows you to attach a file, so you can write whatever you want of whatever length, in whatever format!