Bombich.com is a great source of filesystem feature deep dives. He started with running a backup lab, helped people with corner cases and common failure modes.

Bombich.com is a great source of filesystem feature deep dives. He started with running a backup lab, helped people with corner cases and common failure modes. He created a GUI Mac app to guide people through the gnarly bits, and later contributed metadata patches to rsync, for which I am truly grateful. Back in 2004, I played with file systems, metadata archives, directories with 20,000+ files in them. Learned that at that time, GNU ls had a polynomial-time sort algorithm. I didn't dig into it as much as I should have, but there are sort algorithms that have already-sorted input as worst-case for runtime.