from
The Free On-line Dictionary of Computing (8 July 2008)
mirror site
<networking> An {archive site} or {website} which keeps a
copy of some or all files at another site so as to make them
more quickly available and to reduce the load on the source
site.
It is generally best to use the mirror that is physically
closest to you as this will usually give the fastest download.
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.
(2006-10-16)