Ask HN: How would you design a disk-based web app?

Genuine question: if one were to architect a web app to use disk for storage, rather than a database, how would one do it?

Lately, there's been a lot of buzz about SQLite, and I myself have been impressed with DuckDB. I've also found myself doing my prototyping using plain JSON files on disk, and then "productionizing" to use a database when I need to deploy.

So: suppose I wanted to be able to have multiple web servers - it's nice to be able to create more servers as needed - read and write data to a disk. What would one do? What's the easiest way to share files across multiple servers? How do you ensure you have enough disk? Or partition traffic?