7.8 Considerations for Quorum Mode
The quorum is an important component for any WSFC high availability solution. If you deploy any of the Microsoft SQL Server 2016 AlwaysOn solutions, you can take advantage of the newer quorum models available in Windows Server 2008 or later. The quorum models are as follows:
• Node Majority – This model requires an odd number of nodes and is less common.
• Node and Disk Majority – This is a combination of Node and Quorum disk. This quorum model requires using an RDM for the quorum disk. This is not ideal due to the limitations of RDM disks.
• Node and File Share Majority – This model uses a combination of node and file share as witness. This is recommended for deploying AlwaysOn on vSphere.
• No Majority: Disk Only – This is the traditional Windows Server 2003 quorum disk model. VMware recommends discontinuing use of this model.
Because each customer architecture is different, consider the specific use case when deciding which quorum model is most appropriate for a specific solution. The Node Majority and the Node and File Majority models do not require an RDM disk for the quorum. This could provide additional flexibility and compatibility with vSphere, because vSphere vMotion, DRS, and HA features are fully supported when deploying AlwaysOn Availability Groups with these quorum modes.
See
Understanding Quorum Configurations in a Failover Cluster at
https://technet.microsoft.com/en-us/library/cc731739.aspx for additional information about choosing the appropriate quorum model for the cluster architecture.