The Collaborative International Dictionary of English v.0.48:

Mirror \Mir"ror\, v. t. [imp. & p. p. Mirrored; p. pr. & vb.
   n. Mirroring.]
   1. To reflect, as in a mirror.
      [1913 Webster]

   2. To copy or duplicate; to mimic or imitate; as, the files
      at Project Gutenberg were mirrored on several other ftp
      sites around the world.
      [PJC]

   3. To have a close resemblance to; as, his opinions often
      mirrored those of his wife.
      [PJC]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "mirroring":
   companion, copy, copying, counterfeiting, dead ringer, double,
   duplicate, effigy, emulation, exact likeness, fakery, fellow,
   following, forgery, hit-off, icon, idol, image, imitation,
   impersonation, imposture, impression, likeness, living image,
   living picture, match, mate, mimesis, miniature, model,
   onomatopoeia, parody, photograph, picture, plagiarism, plagiary,
   portrait, reflection, repetition, resemblance, rubbing, semblance,
   shadow, similitude, simulacrum, simulation, spit and image,
   spitting image, takeoff, trace, tracing, twin, very image,
   very picture



The Free On-line Dictionary of Computing (30 December 2018):

mirror
mirroring

   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 backups from a single disk to
   magnetic tape.

   2. mirror site.

   (1998-06-11)