Mirroring offers several benefits:
When an arbiter is present, failover from primary to mirror is automatic. If you are running in synchronous mode, no committed transactions are lost during failover.
Failover is very fast because the mirror server has already applied the transaction log. When the mirror detects that the primary has failed, it rolls back any uncommitted transactions and then makes the database available.
No special hardware, such as a shared disk is required.
No special software (for clustering, for example) is required.
No particular operating system version is required.
The servers do not need to be located near each other geographically. In fact, locating them far apart provides additional protection against disasters such as fire.
Database servers in a mirroring system can also be used to run other databases.