vSphere 6 Fault Tolerance

VMware vSphere Fault Tolerance (FT) provides continuous availability for applications on virtual machines.

FT creates a live clone instance of a virtual machine that is always up-to-date with the primary virtual machine. In the event of a host/hardware failure, vSphere Fault Tolerance will automatically trigger a failover, ensuring zero downtime and data loss. VMware vSphere Fault Tolerance utilized heartbeats between the primary virtual machine and the live clone to ensure availability. In case of a failover, a new live clone will be created to deliver continuous protection for the VM.

The VMware vSphere Fault Tolerance FAQ can be found here.

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On a first glance, VMware vSphere Fault Tolerance seems like a great addition to vSphere HA Clusters to ensure continuous availability within your VMware vSphere environment.

However, in VMware vCenter Server 4.x and 5.x only one virtual CPU per protected virtual machine is supported. If your VM uses more than one virtual CPU, you will not be able to enable VMware vSphere Fault Tolerance on this machine. Obviously, this is an enormous short-come and explains why many companies are not using VMware’s FT capability.

So what’s new with vSphere 6 in regards to Fault Tolerance?

  • Up to 4 virtual CPUs per virtual machine
  • Up to 64 GB RAM per virtual machine
  • HA, DRS, DPM, SRM and VDS are supported
  • Protection for high performance multi-vCPU VMs
  • Faster check-pointing to keep primary and secondary VM in sync
  • VMs with FT enabled, can now be backed up with vStorage APIs for Data Protection (VADP)

With the new features in vSphere 6, Fault Tolerance will surely get much more traction, since you can finally enable FT on VMs with up to 4 vCPUs.