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Encyclopedia > Mirror (computing)

A mirror in computing is a direct copy of a data set. On the Internet, a mirror site is an exact copy of another Internet site. Mirror sites are most commonly used to provide multiple sources of the same information, and are of particular value as a way of providing reliable access to large downloads. Mirroring is a one-way operation whereas file synchronization is two-way. Image File history File links Please see the file description page for further information. ... A mirrored server contains two versions of the same data. ... Memory (Random Access Memory) Look up computing in Wiktionary, the free dictionary. ... In general, data consist of propositions that reflect reality. ... This article is about the computer terms. ... File synchronization (or syncing) in computing is the process of making sure that two or more locations contain the same up-to-date files. ...


A live mirror is automatically updated as soon as the original is changed.

Contents

Reasons

Mirroring of sites occurs for a variety of reasons:

  • To protect data from failure, usually in hardware. See disk mirror.
  • To preserve a website or page, especially when it is closed or is about to be closed.
  • To allow faster downloads for users at a specific geographical location. For example, a U.S. server could be mirrored in Japan, allowing Japanese Internet users to download content faster from the local Japanese server than from the original American one. This may be viewed as caching on a worldwide scale.
  • To counteract censorship and promote freedom of information. For example, an activist might post pictures on a website of a company conducting illegal activities or make available information on secret government activity and be litigated for such. Other internet users will make the content in question available on other servers when the legal action results in the cancellation of ISP or DNS services for the original activist.
  • To provide access to otherwise unavailable information. For example, when the popular Google search engine was banned in 2002 by the People's Republic of China, the mirror elgooG was used as a way of effectively circumventing the ban.
  • To preserve historic content. Financial constraints and/or bandwidth prevent the maintainers of a server from keeping older and unsupported content available to users who still may desire them - a mirror may be made to prevent this content from disappearing.
  • To balance load. If one server is extremely popular a mirror may help relieve this load: for example if a Linux distribution is released as an ISO image onto the distribution developer's own server, this server may become overloaded with demand. Alternative download points allow the total number of download requests to be spread among several servers, maintaining the availability of the distribution.
  • As a temporary measure to counterbalance a sudden, temporary increase in traffic. For example, Slashdotted websites will often be mirrored by a few slashdot posters until the article is pushed off the front page.
  • To increase a site's ranking in a search engine by placing hyperlinks from each mirror to every other mirror (a technique known as link farming). This is viewed as unethical by most search engine administrators and websurfers.
  • Rarely, as a form of plagiarism; this is, however, usually pointless, as a website popular enough to be worth plagiarizing will quickly discover the copy as soon as one of their many readers stumbles onto the plagiarized site.
  • As a form of raising advertising revenue. Wikipedia is probably the best example of material released under the GNU Free Documentation License which is then duplicated by other companies which, unlike Wikipedia, then attempt to generate money from advertising, etc. See Wikipedia:Mirrors and forks. An example of this is the television article, which is mirrored at
http://omniknow.com/common/wiki.php?in=en&term=Television
http://www.startlearningnow.com/TV.htm
http://www.yourart.com/research/encyclopedia.cgi?subject=/television
http://www.internet-encyclopedia.org/wiki.php?title=Television
http://www.everybase.com/Television
http://www.nationmaster.com/encyclopedia/Television
  • To serve as a method of circumventing firewalls.

In data storage, a disk mirror is a complete separate copy of a data set. ... Motto: (Out Of Many, One) (traditional) In God We Trust (1956 to date) Anthem: The Star-Spangled Banner Capital Washington D.C. Largest city New York City None at federal level (English de facto) Government Federal constitutional republic  - President George Walker Bush (R)  - Vice President Dick Cheney (R) Independence from... This article is about the computer term. ... Censorship is the removal or withholding of information from the public by a controlling group or body. ... Freedom of information can mean: whether a particular piece of information can be freely created, read, modified, copied and distributed; see free content (as well as free culture and free software) freedom to express ones opinions or ideas, generally, within a society; see freedom of speech the accessibility of... Activism, in a general sense, can be described as intentional action to bring about social or political change. ... A lawsuit is a civil action brought before a court in order to recover a right, obtain damages for an injury, obtain an injunction to prevent an injury, or obtain a declaratory judgment to prevent future legal disputes. ... “ISP” redirects here. ... “DNS” redirects here. ... Google, Inc. ... For album titles with the same name, see 2002 (album). ... elgooG Logo The correct title of this article is . ... Linux (IPA pronunciation: ) is a Unix-like computer operating system family. ... An ISO image (.iso) is an informal term for a disk image of an ISO 9660 file system. ... Example graph of web traffic at Wikipedia in December 2004 Web traffic is the amount of data sent and received by visitors to a web site. ... The Slashdot effect is the term given to the phenomenon of a popular website linking to a smaller site, causing the smaller site to slow down or even temporarily close due to the increased traffic. ... Slashdot, often abbreviated as /., is a technology-related news website which features user-submitted and editor-evaluated current affairs news with a nerdy slant. ... Google search is the worlds most popular search engine. ... A hyperlink, or simply a link, is a reference in a hypertext document to another document or other resource. ... On the World Wide Web, a link farm is any group of web pages that all hyperlink to every other page in the group. ... Ethics (from the Ancient Greek Ä“thikos, the adjective of Ä“thos custom, habit), a major branch of philosophy, is the study of values and customs of a person or group and covers the analysis and employment of concepts such as right and wrong, good and evil, and responsibility. ... Plagiarism is the unauthorized use or close imitation of the language and thoughts of another author and the representation of them as ones own original work. ... Wikipedia - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... GNU logo (similar in appearance to a gnu) The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft license for free content, designed by the Free Software Foundation (FSF) for the GNU project. ...

Examples

A good example of mirroring is the well-known SourceForge.net website. The basis of the Sourceforge concept is, primarily, the hosting of open-source software projects, but secondarily the use of many different locations to achieve one goal: to maintain download availability to the user. Many innovative computer projects host their sites and software on SourceForge, which provides mirrors in several states and countries, from Dublin, Ireland to Tokyo, Japan. ‹ The template below has been proposed for deletion. ... Open source software is an antonym for closed source software and refers to any computer software whose source code is available under a license (or arrangement such as the public domain) that permits users to study, change, and improve the software, and to redistribute it in modified or unmodified form. ... A BlueGene supercomputer cabinet. ... A state is a set of institutions that possess the authority to make the rules that govern the people in one or more societies, having internal and external sovereignty over a definite territory. ... This article describes a type of political entity. ... WGS-84 (GPS) Coordinates: 53. ... This article or section does not adequately cite its references or sources. ...


Examples of even larger mirrored networks include those of the Debian and FreeBSD software projects. The encyclopedia Wikipedia is mirrored at numerous locations. Debian is a project based around the development of a free, complete operating system through the collaboration of volunteers from around the world. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... Wikipedia - Wikipedia, the free encyclopedia /**/ @import /skins-1. ...


Programs

There are numerous offline browsers that provide automated mirroring of entire sites. Some are oriented towards personal use, which allows browsing from a local copy — this means an initial waiting time but much improved load time for those pages once they're mirrored. Many modern web browsers have a mode called offline browsing, where links to web pages are redirected to local copies in a temporary folder. ...


Other programs are intended to be used by public mirror maintainers.

The correct title of this article is . ... CVSup is a is a computer program which synchronises files and directories from one location to another while minimizing data transfer using file-type specific delta encoding when appropriate. ...

See also


  Results from FactBites:
 
Mirror (computing) - definition of Mirror (computing) in Encyclopedia (584 words)
A mirror in computing is a direct copy of a data set.
Mirror sites are most commonly used to provide multiple sources of the same information, and are of particular value as a way of providing reliable access to large downloads.
If one server is extremely popular a mirror may help relieve this load: for example if a Linux distribution is released as an ISO image onto the distribution developer's own server, this server may become overloaded with demand.
  More results at FactBites »

 
 

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