A duplicate of the contents of a server on a network. Users asking for the data located on the mirrored server are then redirected (automatically or manually) to a mirror that is network-topologically closer to them, thereby relieving network load.

Mirroring is also used on servers and individual hard drives in conjunction with a load-balancing device to establish a form of distributed computing: incoming service requests are distributed between the available resources by the load-balancing device.