Mirroring Levels
Mirroring runs in three distinct modes, each with a specific role. I??™m going to say that
again: mirroring runs in three distinct modes, each with a specific role. If you want to
use database mirroring effectively, you must first burn that fact into your brain. Contrary
to what you may hear, database mirroring doesn??™t necessarily have to do with
high availability.
Only one of the three mirroring modes provides a truly robust means of automated
failover. The other two mirroring modes focus on providing a standby of sorts; one is concerned
with performance, the other with data protection. While often labeled differently
in the interface, the three mirroring modes are generally referred to as High Performance,
High Protection, and High Availability.
Mirroring Mode:High Performance
When you select High Performance, SQL Server configures the connection such that all
communication will be asynchronous. The goal of the High Performance mode is to keep
the principal database performing as efficiently as possible. Records inserted into the
principal are sent to the mirror, but not necessarily on a real-time basis.
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