1.To create a site on a network which is a duplicate of another site, so more users can access a busy site. The closest mirror site to the user will provide the fastest access.
2.To write data to two or more disks or other storage devices, in case one copy is lost
Definition for: mirror site
A duplicate of a busy archive site, which is maintained in order to reduce the load on the source site and to speed up access for users close to the mirror site..