Installing SQL Server service packs and cumulative update packs in a clustered environment

There are some misconceptions about the update process when dealing with a failover cluster.  If the appropriate services are running on each node, you do not have to run the installation on the passive nodes.  The installer will update the components that are node-specific (client tools, SSIS, etc) on the passive nodes first, before completing the cluster-aware components (SQL Services, SSAS) and local components on the active node.

If a mistake is made during installation and services are turned off, you may need to update those local components individually.  But this should not be necessary if the correct steps are taken.

As with any installation, take backups of everything and place them on separate storage in case of a critical failure.  This should include:

- All databases

- The Service Master Key

- Any Analysis Service files

- The registry; if possible, take a complete system backup


The following tasks should also be performed:

- Disable any DDL triggers

- Pause mirroring

- Make sure named pipes is enabled


These services need to be started:

MSDTC - As a clustered resource.  A vital component of failover clustering.

On each node:

Com+ System Application Service - controls the COM+ event system.

Task Scheduler

Cryptographic Service - Handles the database catalog service and controls installation signatures

Remote registry service - required for remote computers to make registry modifications, as in an active node updating the registry of a passive node.

Do not stop any sql services or take any resources offline. 

Execute the installation files on the active node.  Once the process begins, the installer will first update the passive nodes...



...before finalizing the active node and finishing with the cluster-aware services.   This can take a while, so don't panic just yet.

Once the entire installation is complete, reboot the passive node(s).

When they are back online, move the resource groups to each node to verify services are functional. 

Finally, reboot the original active node.  Move the resource groups back.


One final note: Service packs and cumulative updates have been known to modify authentication settings on the SQL Server without any indication.  Double-check to make sure this hasn't occurred on your instance after the installation is complete.