What is that 30GB made up of? If it is simple media files, then hosting them locally is probably easy. If it is something more comlex, like big SCORM packages, then things will be more difficult.
If you just have big videos, then the simple way is to not upload them to Moodle at all. Instead put them on an ordiary web server, and just link to them from Moodle. Give that server a name like http://content.local/, and fix your DNS so that on every site, that URL points to a machine on the local network that has a copy of the video files.