File server
Encyclopedia
In computing, a file server is a computer attached to a network that has the primary purpose of providing a location for shared disk access, i.e. shared storage of computer files (such as documents, sound files, photographs, movies, images, databases, etc.) that can be accessed by the workstations that are attached to the computer network. The term server highlights the role of the machine in the client–server scheme, where the clients are the workstations using the storage. A file server is not intended to perform computational tasks, and does not run programs on behalf of its clients.
It is designed primarily to enable the storage and retrieval of data while the computation is carried out by the workstations.
File servers are commonly found in schools and offices and rarely seen in local internet service providers using LAN to connect their client computers.
File servers may also be categorized by the method of access: Internet file servers are frequently accessed by File Transfer Protocol
(FTP) or by HTTP (but are different from web server
s, that often provide dynamic web content in addition to static files). Servers on a LAN are usually accessed by SMB
/CIFS protocol (Windows
and Unix-like
) or NFS protocol (Unix-like systems). Database server
s, that provide access to a shared database via a database device driver, are not regarded as file servers. Many file servers are simultaneously print server
s too, as they provide access to printers via network. A single file serving computer may be accessible by multiple means: it may run an FTP server, an SMB server, etc., serving the same files.
, 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 fashion compatible
with the older machinery. To manage throughput
, peak loads, and response time
, vendors may utilize queuing theory to model how the combination of hardware and software will respond over various levels of demand. Servers may also employ dynamic load 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 the hard disk drive. Although other forms of storage are viable (such as magnetic tape
and solid-state drives) disk drives have continued to offer the best fit for cost, performance, and capacity.
. A disk array typically has cache
(temporary memory storage that is faster than the magnetic disks), as well as advanced functions like RAID
and storage virtualization
. Typically disk arrays increase level of availability
by using redundant components other than RAID, such as power supplies. Disk arrays may be consolidated or virtualized in a storage area network
(SAN).
providing data access to heterogeneous
clients. NAS devices specifically are distinguished from file servers generally in a NAS being a computer 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.
NAS devices are gaining popularity, offering a convenient method for sharing files between multiple computers. Potential benefits of network-attached storage, compared to non-dedicated file servers, include faster data access, easier administration, and simple configuration.
NAS systems are networked appliances
containing one or more hard drives, often arranged into logical, redundant storage containers or RAID
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 as NFS, SMB/CIFS (Server Message Block/Common Internet File System), or AFP
.
, Novell's eDirectory
or Microsoft's Active 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 can take place directly to the server itself.
It is designed primarily to enable the storage and retrieval of data while the computation is carried out by the workstations.
File servers are commonly found in schools and offices and rarely seen in local internet service providers using LAN to connect their client computers.
Types of file servers
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 and databases.File servers may also be categorized by the method of access: Internet file servers are frequently accessed by File Transfer Protocol
File Transfer Protocol
File Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
(FTP) or by HTTP (but are different from web server
Web server
Web server can refer to either the hardware or the software that helps to deliver content that can be accessed through the Internet....
s, that often provide dynamic web content in addition to static files). Servers on a LAN are usually accessed by SMB
Server Message Block
In computer networking, Server Message Block , also known as Common Internet File System operates as an application-layer network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an...
/CIFS protocol (Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
) or NFS protocol (Unix-like systems). Database server
Database server
A database server is a computer program that provides database services to other computer programs or computers, as defined by the client–server model. The term may also refer to a computer dedicated to running such a program...
s, that provide access to a shared database via a database device driver, are not regarded as file servers. Many file servers are simultaneously print server
Print server
A print server, or printer server, is a device that connects printers to client computers over a network. It can accept print jobs from the computers and send the jobs to the appropriate printers....
s too, as they provide access to printers via network. A single file serving computer may be accessible by multiple means: it may run an FTP server, an SMB server, etc., serving the same files.
Design of file servers
In modern businesses the design of file servers is complicated by competing demands for storage space, access speed, recoverability, ease of administration, securitySecurity
Security is the degree of protection against danger, damage, loss, and crime. Security as a form of protection are structures and processes that provide or improve security as a condition. The Institute for Security and Open Methodologies in the OSSTMM 3 defines security as "a form of protection...
, 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 fashion compatible
Computer compatibility
A family of computer models is said to be compatible if certain software that runs on one of the models can also be run on all other models of the family. The computer models may differ in performance, reliability or some other characteristic...
with the older machinery. To manage throughput
Throughput
In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node...
, peak loads, and response time
Response time
In technology, response time is the time a system or functional unit takes to react to a given input.- Data processing :In data processing, the response time perceived by the end user is the interval between the instant at which an operator at a terminal enters a request for a response from a...
, vendors may utilize queuing theory to model how the combination of hardware and software will respond over various levels of demand. Servers may also employ dynamic load balancing
Load balancing
Load balancing or load distribution may refer to:*Load balancing , balancing a workload amongst multiple computer devices*Load balancing , the storing of excess electrical power by power stations during low demand periods, for release as demand rises*Weight distribution, the apportioning of weight...
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 the hard disk drive. Although other forms of storage are viable (such as magnetic tape
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
and solid-state drives) disk drives have continued to offer the best fit for cost, performance, and capacity.
Storage
Since the crucial function of a file server is storage, technology has been developed to operate multiple disk drives together as a team, forming a disk arrayDisk array
A disk array is a disk storage system which contains multiple disk drives. It is differentiated from a disk enclosure, in that an array has cache memory and advanced functionality, like RAID and virtualization.Components of a typical disk array include:...
. A disk array typically has cache
Cache
In computer engineering, a cache is a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere...
(temporary memory storage that is faster than the magnetic disks), as well as advanced functions like RAID
RAID
RAID is a storage technology that combines multiple disk drive components into a logical unit...
and storage virtualization
Storage Virtualization
Storage virtualization or storage virtualisation is a concept and term used within computer science. Specifically, storage systems may use virtualization concepts as a tool to enable better functionality and more advanced features within the storage system.Broadly speaking, a 'storage system' is...
. Typically disk arrays increase level of availability
Availability
In telecommunications and reliability theory, the term availability has the following meanings:* The degree to which a system, subsystem, or equipment is in a specified operable and committable state at the start of a mission, when the mission is called for at an unknown, i.e., a random, time...
by using redundant components other than RAID, such as power supplies. Disk arrays may be consolidated or virtualized in a storage area network
Storage area network
A storage area network is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices...
(SAN).
Network-attached storage
Network-attached storage (NAS) is file-level computer data storage connected to a computer networkComputer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
providing data access to heterogeneous
Heterogeneous computing
Heterogeneous computing systems refer to electronic systems that use a variety of different types of computational units. A computational unit could be a general-purpose processor , a special-purpose processor Heterogeneous computing systems refer to electronic systems that use a variety of...
clients. NAS devices specifically are distinguished from file servers generally in a NAS being a computer appliance
Computer appliance
A computer appliance is generally a separate and discrete hardware device with integrated software , specifically designed to provide a specific computing resource. These devices became known as "appliances" because of their similarity to home appliances, which are generally "closed and sealed" –...
– 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.
NAS devices are gaining popularity, offering a convenient method for sharing files between multiple computers. Potential benefits of network-attached storage, compared to non-dedicated file servers, include faster data access, easier administration, and simple configuration.
NAS systems are networked appliances
Computer appliance
A computer appliance is generally a separate and discrete hardware device with integrated software , specifically designed to provide a specific computing resource. These devices became known as "appliances" because of their similarity to home appliances, which are generally "closed and sealed" –...
containing one or more hard drives, often arranged into logical, redundant storage containers or RAID
RAID
RAID is a storage technology that combines multiple disk drive components into a logical unit...
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 as NFS, SMB/CIFS (Server Message Block/Common Internet File System), or AFP
Apple Filing Protocol
The Apple Filing Protocol is a network protocol that offers file services for Mac OS X and original Mac OS. In Mac OS X, AFP is one of several file services supported including Server Message Block , Network File System , File Transfer Protocol , and WebDAV...
.
Security
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 to what is known as directory services such as openLDAPOpenLDAP
OpenLDAP Software is a free, open source implementation of the Lightweight Directory Access Protocol developed by the OpenLDAP Project. It is released under its own BSD-style license called the OpenLDAP Public License. LDAP is a platform-independent protocol. Several common Linux distributions...
, Novell's eDirectory
Novell eDirectory
Novell eDirectory is an X.500-compatible directory service software product initially released in 1993 by Novell for centrally managing access to resources on multiple servers and computers within a given network...
or Microsoft's Active Directory
Active Directory
Active Directory is a directory service created by Microsoft for Windows domain networks. It is included in most Windows Server operating systems. Server computers on which Active Directory is running are called domain controllers....
.
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 can take place directly to the server itself.
See also
- BackupBackupIn information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....
- File Transfer ProtocolFile Transfer ProtocolFile Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
(FTP) - Server Message BlockServer Message BlockIn computer networking, Server Message Block , also known as Common Internet File System operates as an application-layer network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an...
(SMB) - Network-attached storageNetwork-attached storageNetwork-attached storage is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements...
(NAS)