In computing, afile server (orfileserver) is acomputer attached to anetwork that provides a location forshared disk access, i.e. storage of computer files (such as text, image, sound, video) that can be accessed by workstations within a computer network. The term server highlights the role of the machine in the traditionalclient–server scheme, where the clients are the workstations using the storage. A file server does not normally perform computational tasks or run programs on behalf of its client workstations (in other words, it is different from e.g. anapplication server, which is another type of server).
File servers are commonly found in schools and offices, where users use alocal area network to connect their client computers.
A file server may be dedicated or non-dedicated. A dedicated server is designed specifically for use as a file server, with workstations attached for reading and writing files anddatabases.
File servers may also be categorized by the method of access: Internet file servers are frequently accessed by File Transfer Protocol or byHTTP (but are different fromweb servers, that often provide dynamic web content in addition to static files). Servers on a LAN are usually accessed bySMB/CIFS protocol (Windows andUnix-like) orNFS protocol (Unix-like systems).
Database servers, that provide access to a shared database via a database device driver, are not regarded as file servers even when the database is stored in files, as they are not designed to provide those files to users and tend to have differing technical requirements.
In modern businesses, the design of file servers is complicated by competing demands for storage space, access speed,recoverability, ease of administration,security, and budget. This is further complicated by a constantly changing environment, where new hardware and technology rapidly obsolesces old equipment, and yet must seamlessly come online in a fashioncompatible with the older machinery. To managethroughput, peak loads, andresponse time,vendors may utilize queuing theory[1] to model how the combination of hardware and software will respond over various levels of demand. Servers may also employ dynamicload balancing scheme to distribute requests across various pieces of hardware.
The primary piece of hardware equipment for servers over the last couple of decades has proven to be thehard disk drive. Although other forms of storage are viable (such asmagnetic tape andsolid-state drives) disk drives have continued to offer the best fit for cost, performance, and capacity.
Since the crucial function of a file server is storage, technology has been developed to operate multiple disk drives together as a team, forming adisk array. A disk array typically hascache (temporary memory storage that is faster than the magnetic disks), as well as advanced functions likeRAID andstorage virtualization. Typically disk arrays increase level ofavailability by using redundant components other than RAID, such aspower supplies. Disk arrays may be consolidated or virtualized in aSAN.
Network-attached storage (NAS) is file-levelcomputer data storage connected to acomputer network providing data access to aheterogeneous group of clients. NAS devices specifically are distinguished from file servers generally in a NAS being acomputer appliance – a specialized computer built from the ground up for serving files – rather than a general purpose computer being used for serving files (possibly with other functions). In discussions of NASs, the term "file server" generally stands for a contrasting term, referring to general purpose computers only.
As of 2010[update] NAS devices are gaining popularity, offering a convenient method for sharing files between multiple computers.[2] Potential benefits of network-attached storage, compared to non-dedicated file servers, include faster data access, easier administration, and simple configuration.[3]
NAS systems are networkedappliances containing one or more hard drives, often arranged into logical, redundant storage containers orRAID arrays. Network Attached Storage removes the responsibility of file serving from other servers on the network. They typically provide access to files using network file sharing protocols such asNFS, SMB/CIFS (Server Message Block/Common Internet File System), orAFP.
File servers generally offer some form of system security to limit access to files to specific users or groups. In large organizations, this is a task usually delegated todirectory services, such asopenLDAP, Novell'seDirectory or Microsoft'sActive Directory.
These servers work within the hierarchical computing environment which treat users, computers, applications and files as distinct but related entities on the network and grant access based on user or group credentials. In many cases, the directory service spans many file servers, potentially hundreds for large organizations. In the past, and in smaller organizations, authentication could take place directly at the server itself.