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The following CPU and networking requirements apply to FT
CPUs that are used in host machines for fault tolerant VMs must be compatible with vSphere vMotion or improved with Enhanced vMotion Compatibility. Also, CPUs that support Hardware MMU virtualization (Intel EPT or AMD RVI) are required. The following CPUs are supported.
- Intel Sandy Bridge or later. Avoton is not supported. AMD Bulldozer or later.
- Use a 10-Gbit logging network for FT and verify that the network is low latency. A dedicated FT network is highly recommended.
FT and legacy FT are not supported in vSphere Essentials and vSphere Essentials Plus.
What happens if vCenter Server is offline when a failover event occurs?
When Fault Tolerance is configured for a virtual machine, vCenter Server need not be online for FT to work. Even if vCenter Server is offline, failover still occurs from the Primary to the Secondary virtual machine. Additionally, the spawning of a new Secondary virtual machine also occurs without vCenter Server.
How many virtual CPUs can I use on a Fault Tolerant virtual machine ?
vCenter Server 4.x and vCenter Server 5.x support 1 virtual CPU per protected virtual machine. vCenter Server 6.0 is supported up to 4 CPUs, depending on licensing.
What happens during a failure?
When a host running the Primary virtual machine fails, a transparent failover occurs to the corresponding Secondary virtual machine. During this failover, there is no data loss or noticeable service interruption. In addition, VMware HA automatically restores redundancy by restarting a new Secondary virtual machine on another host. Similarly, if the host running the Secondary virtual machine fails, VMware HA starts a new Secondary virtual machine on a different host. In either case there is no noticeable outage.