Database mirroring and log shipping are two different technologies
that can be deployed independently or together to mutually complement each other.
The primary reason for using both technologies at the same time
is the limitation that only one mirror server is definable per database.
Hence, if your high availability strategy
is in need of multiple standby databases for extra resiliency in your landscape,
then you will need log shipping deployed, too.
Additionally, log shipping gives you the ability to control the latency
when applying a transaction log in log shipping,
which cannot be controlled with mirroring.
A typical landscape for this configuration can be seen in Figure 27-13.
On the left, the landscape is up and running properly.
On the right, the principal has failed,
and the mirror has become the new principal and is now the log shipping.
Source:
Microsoft SQL 2005 Administrator's Companion,
Chapter 27 - Log Shipping and Database Mirroring
Page 891