1. < hardware , storage > 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 .
(1998-06-11)