Mirror (computing) - Citizendia

In computing, a mirror is an exact copy of a data set. Computing is usually defined like the activity of using and developing Computer technology Computer hardware and software. Debt AIDS Trade in Africa (or DATA) is a Multinational non-government organization founded in January 2002 in London by U2 's On the Internet, a mirror site is an exact copy of another Internet site. The Internet is a global system of interconnected Computer networks 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. To download is to receive data from a remote or central system such as a Webserver, FTP server, mail server or other similar systems Mirroring is a type of file synchronization. File synchronization (or 'synching' 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.

This article does not cover a disk mirror, which is a set of two hard disks containing the same data for fault-tolerance. In Data storage, disk mirroring or RAID1 is the replication of logical disk volumes onto separate physical Hard disks in real time A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device This article contains specific implementations of fault tolerant systems If one of the hard drives fails, all of the data are protected from loss. Those disks are automatically updated together. This scheme is also called RAID1. See also RAID The standard RAID levels are a basic set of RAID configurations and employ striping, mirroring or parity

1 Reasons
2 Examples
3 Programs
4 See also

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. The United States of America —commonly referred to as the For a topic outline on this subject see List of basic Japan topics. This may be viewed as caching on a worldwide scale. In Computer science, a cache (kæʃ like "cash") is a collection of data duplicating original
To counteract censorship and promote freedom of information. Censorship is the suppression of speech or deletion of communicative material which may be considered objectionable harmful or sensitive as determined by a censor Freedom of information (or information freedom) may refer to the accessibility of government-held information ( Freedom of information legislation 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. Activism, in a general sense can be described as intentional action to bring about social or political change In law a lawsuit is a civil action brought before a Court in which the party commencing the action the Plaintiff, seeks a legal or equitable remedy 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. An Internet service provider ( ISP, also called Internet access provider or IAP) is a company which primarily offers their customers access to the Internet The Domain Name System (DNS is a hierarchical naming system for computers services or any resource participating in the Internet.
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. Google Inc is an American public corporation, earning revenue from advertising related to its Internet search, e-mail, online See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. Talk People's Republic of China) PEOPLE'S REPUBLIC OF CHINA ARTICLE GUIDELINES elgooG ( Google spelled backwards is a Mirror image of the Google search engine
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. Linux (commonly pronounced ˈlɪnəks An ISO image is an Archive file (aka Disk image) of an Optical disc using a conventional ISO ( International Organization for Standardization 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. Metalink is a cross-platform and cross-application open standard/framework/file format for programs that download including Download managers BitTorrent
As a temporary measure to counterbalance a sudden, temporary increase in traffic. Web traffic is the amount of data sent and received by visitors to a Web site. For example, Slashdotted websites will often be mirrored by a few slashdot posters until the article is pushed off the front page. The Slashdot effect, also known as slashdotting, is the phenomenon of a popular Website linking to a smaller site causing the smaller site to slow down or even temporarily Slashdot, often abbreviated as /, is a technology-related news Website owned by SourceForge Inc
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). In computing a hyperlink is a Reference or Navigation element in a Document to another Section of the same document or to another For the discussion about Wikipedia see. On the World Wide Web, a link farm is any group of Web sites that all Hyperlink This is viewed as unethical by most search engine administrators and websurfers. Ethics is a major branch of Philosophy, encompassing right conduct and good life
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. Plagiarism is the unauthorized use or close imitation of the language and thoughts of another author and the representation of them as one's own original work
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. ***************************************************************************************** * * The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software See Wikipedia:Mirrors and forks. An example of this is the television article, which is mirrored at

http://omniknow. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic 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. SourceForgenet is a Source code repository. It acts as a centralized location for software developers to control and manage open source software development Open source software (OSS began as a marketing campaign for Free software. 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. A computer is a Machine that manipulates data according to a list of instructions. A state is a political association with effective Sovereignty over a geographic Area and representing a Population. In Political geography and International politics, a country is a Political division of a geographical entity Dublin (ˈdʌblɨn/ /ˈdʊblɨn or /ˈdʊbəlɪn/, bˠalʲə aːha klʲiəh or cliə(ɸ is both the largest city and capital of Ireland. Ireland (pronounced /ˈaɾlənd/ Éire) is the third largest island in Europe, and the twentieth-largest island in the world officially, is one of the 47 prefectures of Japan and located on the eastern side of the main island Honshū. For a topic outline on this subject see List of basic Japan topics.

Examples of even larger mirrored networks include those of the Debian and FreeBSD software projects. Debian ( pronounced) is a computer Operating system composed entirely of Free and open source software. FreeBSD is a Unix-like free Operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD branch through The encyclopedia Wikipedia is mirrored at numerous locations. ***************************************************************************************** * *

Examples of free file mirroring sites are MassMirror, ShareBee, and ShareOnAll. They allow anyone to mirror any file.

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.

rsync
CVSup

As of Feb, 3rd 2008 the only known free file mirroring software is MMup by MassMirror. rsync is a Software application for Unix systems which synchronizes files and directories from one location to another while minimizing CVSup is a Computer program that synchronizes files and directories from one location to another while minimizing Data transfer using

Contents

Reasons

Examples

Programs

See also