Overview of the failover cluster

A Hyper-V Failover Cluster consists of two or more Hyper-V Server compute nodes. Technically, it's possible to use a Failover Cluster with just one computing node; however, it will not provide any availability advantages over a standalone host and is typically only used for migration scenarios.

Note

I don't recommend you to implement a Hyper-V cluster in production without at least three nodes. A single node cluster doesn't ensure high availability. A two-node cluster is not efficient because half of the resources are dedicated to high availability.

A Failover Cluster hosts roles such as Hyper-V virtual machines on its computing nodes. If one node fails due to a hardware problem, it will no longer perform cluster heartbeat communication, even though the service interruption is almost instantly detected. The virtual machines running on that particular node are powered off immediately because of the hardware failure on their computing node. The remaining cluster nodes then immediately take over these VMs in an unplanned failover process and start them on their own respective hardware. The virtual machines will be a backup, running after a successful boot of their operating systems and applications in just a few minutes. Hyper-V Failover Clusters work on the condition that all compute nodes have access to a shared storage instance, holding the virtual machine configuration data and its virtual hard disks. In the case of a planned failover, that is, for patching compute nodes, it's possible to move running virtual machines from one cluster node to another without interrupting the VM. All cluster nodes can run virtual machines at the same time, as long as there is enough failover capacity running all services when a node goes down. Even though a Hyper-V cluster is still called a Failover Cluster, utilizing the Windows Server Failover Clustering feature, it is indeed capable of running an Active/Active Cluster.

To ensure that all these capabilities of a Failover Cluster are indeed working demands an accurate planning and implementation process.