Q. What is site-awareness in Windows Server 2016 Failover Clustering?
A. In Windows Server 2012 R2 while it was possible to geographically stretch a cluster the cluster itself really had no concept of the different physical locations which meant it was difficult to make services failover to "local" nodes to the current resource location nor was it easy to specify a certain location as the "primary" which should stay active in the event of a split in communication.
Windows Server 2016 introduces site awareness which enables nodes to be grouped based on their physical location. This knowledge of physical location is used in a number of ways:
- When a node fails or needs to be drained the resources are moved to nodes in the same site if possible
- VMs follow the site owning the CSV so if a CSV moves to a new site the VMs will follow within a minute via live migration
- A primary site can be defined that in the event of a split and all other things are equal will maintain quorum and offer services as dynamic quorum prunes nodes from non-preferred site first. The preferred site is also used at startup where VMs will start in preferred site first
- Heartbeats behave differently within a site and between sites instead of being based on IP subnets
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