I generally install SQL 2005 and patch it to SP3. The SP3 patch is a single executable and it is a cumulative patch. Some of the confusions that arises during patching are: Do I patch all the nodes, which node do I patch first, does the server have to be restarted, can SQL be running during the patching process? etc… Here are my ramblings:
Clustering is meant to be a high availability solution. Patching is one of the pro-clustering case scenarios. This means that one of the nodes can be patched, and if it breaks, a fail over to the non-patched working node will save the day. It is suggested to patch the active node first. If there are no issues after patching the active node, then the next node can be patched. SQL can be running during the patching process, but a reboot will be required after patching. If the SQL services are stopped (configuration manager), then a reboot is not required. Please feel free to add any comments if you have any.