To resolve this issue, reboot all of the nodes in the cluster in a staggered fashion, waiting at least 1 second between POST on each cluster node. (A 1 second delay between POST on the cluster nodes will avoid the 16 millisecond window that can lead to duplicate keys). Then run the Cluster Validation tool again. If this Validate Disk Arbitration test continues to fail after a staggered power on or reboot, please contact your storage vendor, as the failure indicates that the storage is not handling arbitration properly. This will be addressed in a future version of Windows.