Ask HN: Resources to learn filesystems/storage

Are there are any good resources to learn file systems specifically and storage domain in general. For e.g. networking has many books and courses for overall view to specific protocols (richard stevens, etc). But I didn't find any good book on filesystems. There are university courses but even MOOCs are low on this subject.

Few resources I could gather are -

* Practical File System Design (pdf available online)

* [CMU's 15-746](https://www.ece.cmu.edu/~ganger/746.fall17/) looks good but it's not accessible to non-CMU

Similarly, there are many books on router design, underlying hardware and protocols but I didn't come across any such book for storage appliances.