It’s been a bit of a hot topic on TechNet: people who upgraded to Windows Server 2008 R2 Service Pack 1 on 3+ node clusters started having issues with cluster validation. Before the upgrade there was no issue. Didier Van Hoye (follow him!) pinged me to alert me to a new KB (KB2531907) that should be out today to fix the issue. Eldin Christensen (one of the seniors behind Failover Clustering) posted on the TechNet forums to alert us.
In the post, Eldin says:
“A hotfix is now available that addresses the Win2008 R2 service pack 1 issue with Validate on a 3+ node cluster. This is KB 2531907. The KB article and download link will be published shortly, in the mean time you can obtain this hotfix immediately free of charge by calling Microsoft support and referencing KB 2531907”.
It’s a pity that you cannot just download it like other publicly available KBs. This is an issue that will cause support issues if you call MS CSS with other clustering problems; remember that CSS supports clusters that pass the validation test.
BTW, this linked article by Didier includes some more fixes to be aware of for W2008 R2 SP1 clusters.
EDIT: Microsoft did post the hotfix online so you can download it.