The dynamic quorum model is the default quorum configuration available when you are creating a Cluster using Windows Server 2012. We can manually remove nodes from participating in the voting. To keep a cluster up and running proper voting and quorum should be maintained. Each node in a cluster is a vote. For the cluster to keep going more than half of the votes must continue to run. That means if there are 7 nodes in a cluster, it requires a minimum of 4 [(7+1)/2] nodes up and running to keep the cluster up.
As per the above example, in windows server 2008 R2 we need to make sure that at least 4 nodes are running to keep the cluster up and if there are only 3 nodes are running then the cluster services will terminate immediately. We need to manually force the cluster to start and bring it online. But in a Windows Server 2012 Failover Cluster when a node goes down the number of votes needed to maintain the cluster also dynamically goes down. So as mentioned in the earlier example if one node goes down, the total vote count becomes 6 and minimum also reduces and the server will continue running. Although dynamic quorum solved the problem of causing the entire cluster to shut down due to lack of quorum voting, it did not eliminate the need to manually configure a witness resource when the node count changes.
In Windows Server 2012 R2 introduced the concept of dynamic witness which dynamically assigns the witness resource a vote, depending on the number of online nodes in the cluster. If the number of nodes are even witness is required and given a vote and if its odd then the witness is removed dynamically from the voting mechanism. When creating a failover cluster with Windows Server 2012 we always configure a witness resource. The Failover clustering feature determines when the witness should have a vote.
As per the above example, in windows server 2008 R2 we need to make sure that at least 4 nodes are running to keep the cluster up and if there are only 3 nodes are running then the cluster services will terminate immediately. We need to manually force the cluster to start and bring it online. But in a Windows Server 2012 Failover Cluster when a node goes down the number of votes needed to maintain the cluster also dynamically goes down. So as mentioned in the earlier example if one node goes down, the total vote count becomes 6 and minimum also reduces and the server will continue running. Although dynamic quorum solved the problem of causing the entire cluster to shut down due to lack of quorum voting, it did not eliminate the need to manually configure a witness resource when the node count changes.
In Windows Server 2012 R2 introduced the concept of dynamic witness which dynamically assigns the witness resource a vote, depending on the number of online nodes in the cluster. If the number of nodes are even witness is required and given a vote and if its odd then the witness is removed dynamically from the voting mechanism. When creating a failover cluster with Windows Server 2012 we always configure a witness resource. The Failover clustering feature determines when the witness should have a vote.
