Disconnected operation (DO) has become one of the important issues for increasing the reliability and performance of distributed computing environment. A good distributed file system should support fundamental system services in case of network or communication failure. The proposed efficient disconnected operation protocol in Storage Area Network (SAN) distributed file system is to provide high performance, high availability, data consistency, increased scalability, automated storage and data management capability to the client, though it is disconnected from the server. Chapter 1 discusses about the preliminary concepts of the file systems, distributed computing, its advantageous features and limitations. Chapter 2 presents on the various locking mechanism in distributed file systems. Chapter 3 focuses on the various authentication mechanisms for the network storage and Chapter 4 discusses about the safe caching mechanism in SAN file system. Chapter 5 proposes a protocol for SAN file system which is disconnected operation oriented. Finally, Chapter 6 contains concluding remarks and also provides some recommendations that can be helpful for future research works.