But what if you need to serve more users? That's where PeerTube's federation feature shines. If other PeerTube instances following yours, chances are they have decided to mirror part of your instance!
Do you want to enable transcoding? If so, do you want to provide multiple resolutions per video? Try this out with a few videos and you will get an idea of how much extra space is required per video and estimate a multiplication factor for future space allocation.