http://lainyubrp2aabmxhepbttfdbl53dct2inqifs42buvpf6w44uiitbeqd.onion/blog/matrix.html
If your users join huge rooms with 10k+ members, the i/o value will be bound to skyrocket. One day, I had 80 LA on VPS with 2 GB ram and 1 core! After that, I moved to a better VPS for the sake of stability. Users media is not a big problem, as it can be cleaned just using find to delete files that have not been used for, lets say, a month.