Limit uploads to something small, like 16MB.
Are videos being uploaded? If so, move videos to a separate video server and link to them from within Moodle.
This sorta falls under 'one solution *does not* fit all'! Much depends ...
Nothing internal like a plugin of which I am aware.
However, this is a tool (command line only) that will help called moosh
and for specific commands related to files
Examples of some of the commands:
Go through all files in Moodle data and check them for corruption. The check is to compare file's SHA to their file names.
Check that all files recorder in the DB do exist in Moodle data directory.
Are you doing autobackups?
Another Moosh example:
Example 4: Remove all automated backups and reclaim the space
moosh file-list -i 'component="backup" AND filearea="automated"' | moosh file-delete -s
moosh file-delete --flush
Are your teachers running backups of their own? Are they cleaning up OLD backups they really no longer need?
One could attempt to use repos for things like videos/audios .. etc.
'spirit of sharing', Ken