Last month Microsoft released an important update that probably escaped your attention – it certainly did mine. The KB article is titled “Validate SCSI Device Vital Product Data (VPD) test fails aver you install Windows Server 2008 R2 SP1”, which didn’t seem to fit any problem that I had experienced. Until I read the details.
The hotfix will fix several different cluster validation issues, but the important part to me is that it fixes an issue where even though you choose to keep the services/applications online when running the cluster validation, the validation incorrectly runs against disks that are being used by those services/applications. Validation then fails because it cannot get a persistent reservation on the disk. Note: it will pass on the node that owns the the disk because it can get a persistent reservation on that node only.
This means that either you can’t add nodes to the cluster, or that you have to take all services/applications offline – which is not very helpful on a production cluster. To resolve this issue, install the hotfix mentioned in this KB article: http://support.microsoft.com/kb/2531907.