If I recall correctly, I don't believe the book covers distributed file systems. For those, I highly recommend reading the research papers describing modern distributed file systems such as HDFS, Google's various storage systems and databases (such as Bigtable and Spanner), and Ceph, making sure to check the bibliographies and read the cited papers to get a better understanding of the background material. That's how I learned the basics of distributed file systems when I worked on a research project involving Ceph back when it was brand new.