Overview of Mirroring:
Mirroring is mainly implemented for increasing the database availability. Similar to log shipping mirroring is also implemented on per database basis. Database mirroring maintains two copies of a single database that must reside on different instances of SQL Server Database Engine (server instances). Typically, these server instances reside on computers in different locations. One server instance serves the database to clients (the principal server), while the other server instance acts as a hot or warm standby server (the mirror server).