Hyper-V vs. VMware vSphere – Fault Tolerance

Windows Server 2012 RC Logo

Virtualization specialist and blogger Marcel van den Berg wrote a interesting blog post comparing high availability in VMware vSphere 5 and Windows Server 2012 Hyper-V with the title vSphere 5 versus Windows Server 2012 Hyper-V: high available VMs. In his blog post he mentions VMware Fault Tolerance, which I think it is a good feature but there are some things you have to be aware of.

VMware vSphere includes a feature called “Fault Tolerance” which allows you to run a hot-standby Virtual Machine on an other VMware vSphere Hypervisor host, which will take over if the primary Virtual Machine fails.

This is a great feature but it also has some disadvantages, because you have to sacrifice on scale and features.

  • No Memory Overcommit (Dynamic Memory)
  • Only 1 vCPU per Fault Tolerance Virtual Machine
  • Maximum 4 Fault Tolerance VMs per host
  • No Snapshots
  • Maximum of 64GB RAM
  • IPv6 is not supported in VMware FT
  • Virtual Machine cannot be replicated with the vSphere Replication (SRM 5)
  • No Hot-plug support for virtual devices
  • No Dynamic Resource Optimization

Now Microsoft does not offer a Fault Tolerance feature in Hyper-V. But offers besides the Hyper-V Failover Clustering some great virtual guest clustering capabilities. But if you need true Zero Fault Tolerance the Microsoft partner Stratus Technologies offers a great solution (ftserver) with a lot less disadvantages.