Network File System Phil Segel Muhammad Kamran Arain Ala F Alnawaiseh Group 3 Outline Introduction Network File System NFS Windows Distributed File System DFS Introduction A Distributed File System DFS is a File System that supports sharing of files and resources in the form of persistent storage over a network The first file servers were developed in the 1970s Sun s Network File System NFS became the first widely used distributed file system after its introduction in 1985 Clients and servers A file server provides file services to clients A client interface for a file service is formed by a set of primitive file operations Creating a file Deleting a file Reading from a file and Writing to a file Distribution A DFS is a file system whose clients servers and storage devices are dispersed among the machines of a Distributed System or intranet Accordingly service activity has to be carried out across the network and instead of a single centralized data repository the system has multiple and independent storage devices The distinctive features of a DFS are the multiplicity and autonomy of clients and servers in the system Transparency Ideally a DFS should appear to its clients to be a conventional centralized file system The multiplicity and dispersion of its servers and storage devices should be made invisible Performance The most important performance measurement of a DFS is the amount of time needed to satisfy service requests In conventional systems this time consists of a disk access time and a small amount of CPUprocessing time In a DFS however a remote access has the additional overhead attributed to the distributed structure Concurrent File Updates A DFS should provide for multiple client processes on multiple machines not just accessing but also updating the same files Concurrency control or locking may be either built into the file system or be provided by an add on protocol Distributed Data Store A Distributed Data Store is a network in which a user stores his or her information on a number of peer network nodes Most of the peer to peer networks do not have distributed data stores in that the user s data is only available when their node is on the network Distributed Data Store Networks FreeNet MNet Andrew File System AFS NNTP BitTorrent The Mnesia Database GNUnet Secure File system SFS Global File System GFS The Chord Project SVK Distributed Version Control Groove shared workspace used for DoHyki Windows Distributed File Systems What is the purpose of Windows DFS To unite files on different computers into a single namespace Make it easy to build a single hierarchal view of multiple file servers and file server shares on your network To display files in a single directory structure regardless of what server the files are on Comparison Windows Distributed File Systems do for servers what a file system does for a hard disk DFS File Protocols Not limited to a single protocol Regardless of client used can support mapping of Servers Shares Files Supports these provided that the client supports the native server and share History The UNC Universal Naming Convention was required to specify the physical server and share to access file information i e Server share path filename Could be used directly by drive mapping i e X path fileame As network continues to grow mapping shares individually scales poorly Solution to historical problems Windows DFS solves these problems by linking physical storage into logical representation Permits shares to be hierarchally connected to other Windows shares Make physical location of data transparent to users and applications DFS Features and Benefits Feature Custom hierarchical view of shared network resources Description By linking shares together administrators can create a single hierarchical volume that behaves as though it were one giant hard drive Individual users can create their own Dfs volumes which in turn can be incorporated by other Dfs volumes These are called inter Dfs links Benefit Provides a simplified view of network shares that can be customized by the administrator DFS Features and Benefits Continued Feature Flexible volume administration Description Individual shares participating in the Dfs volume can be taken offline without affecting the remaining portion of the volume name space Benefit Allows administrators to manage physical network shares independent of their logical representation to users DFS Features and Benefits Continued Feature Graphical administration tool Description Each Dfs root is administered with an easy touse graphical administration tool that permits browsing configuration of volumes alternates and inter Dfs links as well as administration of remote Dfs roots Benefit Requires little training reducing the need for trained full time server administrators DFS Features and Benefits Continued Feature Higher data availability Description Multiple copies of read only shares can be mounted under the same logical Dfs name to provide alternate locations for accessing data If one of the copies becomes unavailable an alternate is automatically selected Benefit Important business data is always available even if a server disk drive or file occasionally fails DFS Features and Benefits Continued Feature Load balancing Description Multiple copies of read only shares on separate disk drives or servers can be mounted under the same logical Dfs name thus permitting limited load balancing between drives or servers As users request files from the Dfs volume they are transparently referred to one of the network shares comprising the Dfs volume Benefit Automatically distributes file access across multiple disk drives or servers to balance loads and improve response time during peak usage periods DFS Features and Benefits Continued Feature Name transparency Description End users navigate the logical name space without consideration to the physical locations of their data Physical data can be relocated to any server and the logical Dfs name space can be reconfigured so that the end user s perspective of the Dfs name space is unaffected that is it is transparent to users that their data has changed location Benefit Increased administrative flexibility Administrators can move network shares between servers or disk drives without affecting users ability to access the data DFS Features and Benefits Continued Feature Integration with Windows NT security model Description No additional administrative or security issues Any user who