Mirror

In computing, a mirror is a server that gives a precise copy of knowledge from one other server. This could also be a number of information, a database, a web site, or a whole server.

Mirroring is designed to supply fault tolerance, or a method of redundancy in case one thing goes fallacious with the first or “principal” server. If principal server unexpectedly goes offline, for instance, the mirror server can take over. This course of could also be carried out mechanically, nevertheless it requires a 3rd system, referred to as a “witness” server. This machine displays each servers and transfers all site visitors to the mirror if an outage is detected with the principal server.

Server mirroring will also be used for deliberate upkeep, comparable to upgrading a server or operating software program updates that require companies to be stopped or restarted. In these situations, a server admin can manually set the mirror because the principal server to keep away from downtime. Some mirroring setups enable “role switching,” by which the principal and mirror servers might be swapped at any time.

Another sort of mirroring – FTP mirroring – merely gives a number of information from a number of servers. For instance, a obtain web page could listing a number of “mirror” URLs, which all supply the identical file. The mirrors are usually listed by geographical location, so you’ll be able to choose the one closest to you. While FTP mirrors nonetheless exist, they’ve pale in recognition as automated location detection and content material supply networks have automated this course of.