Installing SQL Server CU's

Hi,

I've a question on applying cumulative updates to SQL Server, specifically CU7 to fix an issue affecting us.  I've done this in our development and qa instances (all servers have 2-3 instances) and everything is fine so I'm ready to push this out to production.

Our production server is an active/passive cluster so I'm not sure how this will change the process.  I've not had to apply a CU in production before so I don't fully understand the process.  Also, the production server has two instances which are both on the active node.

I've read about taking the passive node out of the cluster group, patching that server, rebooting, failing over and repeating.  What I wasn't sure about was if this applied to CU's as well as Service Packs?  Also, if I'm patching the passive node, won't it ask me for an instance to patch too?

As a final point and something I have suggested is a no go is the request to apply to CU to only one instance (the non-critical one) first and do the second instance on the weekend.  The idea being a bit of a test run on a clustered instance (nobody seems to have done it here previously).  I want to do them together when we are sure of the process.

Thanks