Failover Clustering in Windows Server 2012 R2 – Tie Braker for 50% node split

Beside having ability to use Dynamic quorum for Failover clusters, clustering in Windows Server 2012 R2 is enhanced with one more very interesting functionality.
The cluster is now able to automatically adjust running node’s vote status in order to keep total number of votes in the cluster at odd number. This feature is called Tie breaker for 50% node split and it works together with dynamic witness functionality. Dynamic witness functionality is used to adjust the value of quorum witness vote. For example, if you have a cluster with even number of nodes and a file share witness, if the file share witness fails, cluster will use dynamic witness functionality to automatically remove the vote from file share witness.
However, since the cluster now has even number of votes, cluster tie breaker will randomly pick a node, and remove it quorum vote to maintain odd number of votes. If the nodes are evenly distributed in two sites, this will help to maintain cluster functional in one site. In previous Windows Server versions, if both sites have equal number of nodes and file share witness fails, both sites will stop the cluster.

If you want to avoid node being picked randomly you can use LowerQuorumPriorityNodeID property to predetermine which node will have its vote removed. You can set this property by using following Powershell command:

(Get-Cluster).LowerQuorumPriorityNodeID = 1

,where “1” is the example node ID for a node in the site that you consider less critical.
This will be very nice to use with DR scenarios.

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