I'm using the Course size report plugin to see which courses are taking up a lot of space. But I don't know a convinient way to investigate further. For example, we have a single course taking up 14 gigabytes. The course has dozens and dozens of files, but is there an easy way to see which files are taking up most space? The Course size plugin "summary of plugin types" shows 0 bytes for all plugins.
My solution so far, if it helps someone: unzip a full backup of the course somewhere, then check it with a WinDirStat of similar. Finally I looked from the files.xml which file the hash maps to.
That's what I was going to suggest! But with 'no user data' as an extra element.
I noticed that most of the course data was student submissions. It seems to be the case in most courses.