Had a technical architecture document recently from an external supplier proposing a mirrored SQL Server 2005 setup with the Principal as a MSCS. Noticed in the Technet docs that:
"... you may consider using database mirroring as a method for creating a hot standby for a cluster instance database. If you do, be forewarned that because a cluster failover is longer than the timeout value on database mirroring, a High Availability mode mirroring session will react to a cluster failover as a failure of the principal server. It would then put the cluster node into a mirroring state."
Sooooo... this makes the use of a cluster Principal kind of redundant as if it fails over then SQL will move over to the Mirror server. For further info see the Mirroring FAQ.
"... you may consider using database mirroring as a method for creating a hot standby for a cluster instance database. If you do, be forewarned that because a cluster failover is longer than the timeout value on database mirroring, a High Availability mode mirroring session will react to a cluster failover as a failure of the principal server. It would then put the cluster node into a mirroring state."
Sooooo... this makes the use of a cluster Principal kind of redundant as if it fails over then SQL will move over to the Mirror server. For further info see the Mirroring FAQ.