Subject: Operating System

Topic: DISTRIBUTED SYSTEMS

Difficulty: Hard

A method of storing and accessing files based in a client/server architecture. In a distributed file system, one or more central servers store files that can be accessed, with proper authorization rights, by any number of remote clients in the network. Much like an operating system organizes files in a hierarchical file management system, the distributed system uses a uniform naming convention and a mapping scheme to keep track of where files are located. When the client device retrieves a file from the server, the file appears as a normal file on the client machine, and the user is able to work with the file in the same ways as if it were stored locally on the workstation. When the user finishes working with the file, it is returned over the network to the server, which stores the now-altered file for retrieval at a later time.

Distributed file systems can be advantageous because they make it easier to distribute documents to multiple clients and they provide a centralized storage system so that client machines are not using their resources to store files.

One process involved in implementing the DFS is giving access control and storage management controls to the client system in a centralized way, managed by the servers. Transparency is one of the core processes in DFS, so files are accessed, stored, and managed on the local client machines while the process itself is actually held on the servers. This transparency brings convenience to the end user on a client machine because the network file system efficiently manages all the processes. Generally, a DFS is used in a LAN, but it can be used in a WAN or over the Internet.

A DFS allows efficient and well-managed data and storage sharing options on a network compared to other options. Another option for users in network-based computing is a shared disk file system. A shared disk file system puts the access control on the client’s systems so the data is inaccessible when the client system goes offline. DFS is fault-tolerant and the data is accessible even if some of the network nodes are offline.

A DFS makes it possible to restrict access to the file system depending on access lists or capabilities on both the servers and the clients, depending on how the protocol is designed.