I have an IIS server with hundreds of gigs of static media files (and no dynamic content). I've done what seem to be the usual steps: RAID tuning, reduce logging & debugging, disable unnecessary services, and enable compression.
Regarding compression: Under IIS Manager > SERVERNAME > Compression > Static Compression > Per application pool disk space limit, the default is 100 MB. That's about the size of 1 or 2 videos, so I doubt it helps much.
The question: what happens if you turn this limit way way up? Like to 100 GB? Or would it be better to just turn off compression entirely, since videos are already pretty close to max compression?