Nothing so far. I haven't have time to dig deep into this because getting this 1000 students school running smoothly on Moodle is still fully occupying my days. So far we don't have problems with the storage. One way how we are trying to reduce storage usage from the beginning is that we have advised all our teachers to use YouTube if they want to share their own videos. We have given them permission to add videos into our school YouTube account and we will keep those videos as unlisted so that no one can watch them without exact link. After that our teacher embed those videos into their course page. This solution is good enough for us. So we are not in hurry to find an answer to this question. I will keep you up to date in this threat if something comes up.