mirror
1. Writing duplicate data to more than one
device (usually two {hard disks}), in order to protect against
loss of data in the event of device failure. This technique
may be implemented in either hardware (sharing a {disk
controller} and cables) or in software. It is a common
feature of {RAID} systems.
Several {operating systems} support software disk mirroring or
{disk-duplexing}, e.g. {Novell NetWare}.
See also {Redundant Array of Independent Disks}.
Interestingly, when this technique is used with {magnetic
tape} storage systems, it is usually called "twinning".
A less expensive alternative, which only limits the amount of
data loss, is to make regular {backup}s from a single disk to
{magnetic tape}.
2. An {archive site} or {web site} which keeps a
copy of some or all files at another site so as to make them
more quickly available to local users and to reduce the load
on the source site. Such mirroring is usually done for
specific whole directories or files on a specific remote
server as opposed to a {cache} or {proxy server} which keeps
copies of everything that is requested via it.
For example, src.doc.ic.ac.uk is the main UK mirror for the
{GNU} archive at gnu.org. There are also several
{mirrors of this dictionary
(http://foldoc.doc.ic.ac.uk/foldoc/mirrors.html)}.
(1998-06-11)