In the second part of this book, we will start with the classic case of distributed systems, GFS (Google File System), and gradually guide readers through building the distributed consensus algorithm Raft, based on Raft to construct the distributed key-value storage system eraftkv, and addressing the scalability problem of Raft single-group by implementing Multi-Raft. GFS is designed by Google for large-scale distributed data-intensive applications, featuring a scalable distributed file system. In this chapter, we will begin with GFS to provide readers with a basic understanding of the architecture, reading and writing, consistency, and more in distributed file systems.