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Information about Mirror (computing)

This article is about replicating Internet sites. For mirroring of hard disks, see disk mirroring.
In computing, a mirror 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 type of file synchronization.

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

This article does not cover a disk mirror, which is a set of two hard disks containing the same data for fault-tolerance. If one of the hard drives fails, all data is protected from loss. Those disks are automatically updated together. This scheme is also called RAID1.

Reasons

Mirroring of sites occurs for a variety of reasons:
  • 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. Metalink is frequently used for automatic load balancing by listing all mirrors.
  • 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.

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.

Examples of even larger mirrored networks include those of the Debian and FreeBSD software projects. The encyclopedia Wikipedia is mirrored at numerous locations.

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.

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

See also

In data storage, disk mirroring or RAID1 is the replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability, currency and accuracy.
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computing is synonymous with counting and calculating. Originally, people that performed these functions were known as computers. Today it refers to a science and technology that deals with the computation and the manipulation of symbols.
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For other uses, see Data (disambiguation).


Debt, AIDS, Trade in Africa (or DATA) is a multinational non-government organization founded in January 2002 in London by U2's Bono along with Bobby Shriver and activists from the Jubilee 2000 Drop
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Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government
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Uploading and downloading are related terms used to describe the transfer of electronic data between two computers or similar systems. More colloquially, they are sometimes applied to transfers to/from removable media such as CDs.
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File synchronization (or 'synching') in computing is the process of making sure that two or more locations contain the same up-to-date files. If you add, change, or delete a file from one location, the synchronization process will add, change, or delete the same file at the other
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In data storage, disk mirroring or RAID1 is the replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability, currency and accuracy.
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Hard disk drive

An IBM hard disk drive with the metal cover removed. The platters are highly reflective.
Date Invented: September 13 1956
Invented By: An IBM team led by Reynold Johnson
Connects to:
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Fault-tolerance or graceful degradation is the property that enables a system (often computer-based) to continue operating properly in the event of the failure of (or one or more faults within) some of its components.
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Motto
"In God We Trust"   (since 1956)
"E Pluribus Unum"   ("From Many, One"; Latin, traditional)
Anthem
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Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
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cache (IPA:/kæʃ/, like "catch" [1]) is a collection of data duplicating original values stored elsewhere or computed earlier, where the original data is expensive to fetch (due to longer access time) or to
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Censorship is defined as the removal and/or withholding of information from the public by a controlling group or body.

Typically censorship is done by governments, religious groups, corporations, or the mass media, although other forms of censorship exist.
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Freedom of information may refer to:
  • Whether particular information can be freely created, read, modified, copied and distributed; see Free content (as well as Free culture movement and Free software)
  • Freedom to express one's opinions or ideas,

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Activism, in a general sense, can be described as intentional action to bring about social or political change. This action is in support of, or opposition to, one side of an often controversial argument.
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lawsuit is a civil action brought before a court in which the party commencing the action, the plaintiff, seeks a legal remedy. One or more defendants are required to respond to the plaintiff's complaint.
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Internet service provider (abbr. ISP, also called Internet access provider or IAP) is a business or organization that provides consumers or businesses access to the Internet and related services. In the past, most ISPs were run by the phone companies.
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On the Internet, the Domain Name System (DNS) associates various sorts of information with so-called domain names; most importantly, it serves as the "phone book" for the Internet by translating human-readable computer hostnames, e.g. en.wikipedia.
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Google Inc.

Public (NASDAQ:  GOOG ), (LSE:  GGEA )
Founded Menlo Park, California (September 7 1998[1])
Headquarters Mountain View, California, USA

Key people Eric E.
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20th century - 21st century - 22nd century
1970s  1980s  1990s  - 2000s -  2010s  2020s  2030s
1999 2000 2001 - 2002 - 2003 2004 2005

2002 by topic:
News by month
Jan - Feb - Mar - Apr - May - Jun
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Anthem
March of the Volunteers (义勇军进行曲)
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elgooG is a mirror image (a flipped around image version) of the Google search engine. The page and all results are displayed in reverse. The site is called the "google mirror" as a parody of the term mirror in computing, which usually refers to a copy or backup of another
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Linux (pronunciation: IPA: /ˈlɪnʊks/, lin-uks) is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; its underlying source code can be
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ISO image

File extension: .iso
Uniform Type Identifier: public.iso-image
Type of format: Disk image
Standard(s): ISO 9660

An ISO image (.iso) is a disk image of an ISO 9660 file system.
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Metalink

File extension: .metalink
MIME type: application/metalink+xml
Type of format: File distribution
Extended from: XML

For the telecommunication company, see Metalink Broadband.

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Web traffic is the amount of data sent and received by visitors to a web site. It is a large portion of Internet traffic. This is determined by the number of visitors and the number of pages they visit.
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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.
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This article has been tagged since July 2007.

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search engine is an information retrieval system designed to help find information stored on a computer system. Search engines help to minimize the time required to find information and the amount of information which must be consulted, akin to other techniques for managing
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A hyperlink, is a reference or navigation element in a document to another section of the same document or to another document that may be on a different website.

Hyperlinks are part of the foundation of the World Wide Web created by Tim Berners-Lee, but are not limited to
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This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
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