One of the big changes in Windows Server 2008 Failover Clustering is the new quorum model. In Windows Server 2003, we had only two choices, either the single disk quorum that has been around since NT 4.0 or Majority Node Set (MNS). Actually, there are three if you consider MNS with the File Share Witness (FSW) as a separate option.
In Windows Server 2008 Failover Clustering, administrators now have four choices on how to implement the quorum.
One option is to use Node majority. In this option, a vote is given to each node of the cluster and the cluster will continue to run so long as there are a majority of nodes up and running.
A second option is to use both the nodes and the standard quorum disk. In this option, a common option for two node clusters, each node gets a vote and the quorum, now called a witness disk) also gets a vote. So long as two of the three are running, the cluster will continue. In this situation, the cluster can actually lost the witness disk and still run.
A third option is to use the classic/legacy model and assign a vote to the witness disk only. This type of quroum equates to the well known, tried, and true model that has been used for years.
A fourth option, is, of course, to use the MNS model with a file share witness.
It has been a few days since I have seen the GUI, so I can’t tell you off the top of my head which order they appear in within the GUI.
Two notes that caught my attention the other day when talking about these options is that it is not possible to use DFS as the file share witness and with changes to the quorum there aren’t any checkpoints so there is no longer a need for the -resetquorumlog switch on starting the cluster service.