Slightly OT.

What resources would people here suggest for learning about file systems? I see a lot of new file systems like zfs, btrfs, etc. I looked up for resources but couldn't find anything substantial.

I want to learn how they work so that I can appreciate projects like this and compare them.

I looked into the Build Your Own X repo but didn't find anything. I found a book called Practical File System Design: The BeOS file system but it's apparently dated, and I'm not sure I want too much of a deep dive.