Improving Availability and enhancing Programmability - Microsoft SQL Server 2008 R2 Administration - page 229

The PARTNER TIMEOUT value is referred to as guidance. As a best practice, you must
test partner timeout with different values that are suitable for your network.
4. In a failover cluster environment, it is essential to configure the ENDPOINT , to use
clustered IP addresses and not the IP address on the cluster nodes.
How it works...
In case of system failure, the default action on the failover cluster initiates the failover action
to another node. In such cases, where the high-safety mode with automatic failover is used,
the node that is running the current principal will start the automatic failover within a few
seconds or based on the set up of the PARTNER TIMEOUT value. The DBM fails to mirror
the server, which becomes the principal server for the DBM pair; whereas the WITNESS is
critical to invoke automatic failure mode, which acts on quorum to meet the failover needs.
Immediately, the new principal server rolls forward its copy of the database as quickly as
possible and brings it online as the principal database. In parallel to the database mirroring
action, the cluster failover completes the failover clustered instance that was a principal
server previously, which then becomes the mirror server instance.
In case of the high-performance mode without automatic failure (asynchronous), the failover
cluster will continue functioning as the principal server in the database mirroring session and
in case of an entire cluster problem, we must force the service to the mirror server instance.
Managing Log Shipping scenarios in a
Database Mirroring environment
Log shipping has been part of SQL Server as a core standby feature (backup and restore),
but it is also considered a high-availability feature. However, it cannot be matched to failover
clustering or database mirroring feature.
Like database mirroring, the log shipping feature includes database level protection with no
automatic failover option. It is also possible to implement log shipping in a database mirroring
environment, as both features complement the log sequence number to function.
The SQL Server 2008 R2 high-availability feature enables the database to perform mirroring
and log shipping simultaneously. In this recipe, we will go through the required steps to
manage log shipping in a database mirroring environment.