Symmetric Multi-Processing Fault Tolerance (SMP-FT) has been a long-awaited feature by many VMware customers. With the release of vSphere 6.0, the SMP-FT capability is now finally available and if you want to try out this new feature and see how it works from a "functional" perspective, you can easily do so by running it in a Nested ESXi environment. SMP-FT no longer uses the "record/replay" capability like its younger brother Uniprocessing Fault Tolerance (UP-FT). Instead, SMP-FT now uses a new Fast Checkpointing technique which not only improves the overall performance of its predecessor but also greatly simplifies and reduces additional configurations when running in a Nested ESXi environment.

Disclaimer: Running SMP-FT in a Nested ESXi environment does not replace or substitute actual testing of physical hardware. For any type of performance testing, please test SMP-FT using real hardware.


  • pESXi host running either ESXi 5.5 or 6.0
  • vCenter Server 6.0
  • 2 x Nested ESXi VMs running ESXi 6.0 (vHW9+)
  • Shared storage for the Nested ESXi VMs


Step 1 - Created a Nested ESXi VM using guestOS type "ESXi 5.5/6.0 or later". You will need at least 2 vCPU or greater, 4GB of memory or greater for the installation of ESXi and most importantly, a VMXNET3 network adapter. The reason a VMXNET3 adapter is required is that SMP-FT has a requirement for 10Gbit network connection and the VMXNET3 driver can simulate a 10Gbit connection for a Nested ESXi VM. For further instructions on creating a Nested ESXi VM, please take a look at this article. If you are unable to add VMXNET3 adapter, you may need to first change the guestOS type to "Other 64-bit", add the adapter and then change the guestOS type back.

Step 2 - Install ESXi 6.0 on the Nested ESXi VM and ensure you also have a vCenter Server 6.0 deployed if you have not done so already and add your Nested ESXi instances to a new vSphere Cluster which has vSphere HA enabled.

Step 3 - You will need to enable both vMotion and Fault Tolerance traffic type for the VMkernel interface that you wish to run FT traffic across.

Step 4 - At this point, you can create a real or dummy VM and power it on. Once you have the powered on VM, you can now enable either UP-FT or SMP-FT by right clicking and selecting "Enable Fault Tolerance".

As you can see from the screenshot above, I have successfully enabled FT on a VM with 4vCPU running inside of a Nested ESXi VM, how cool is that!? Hopefully this will help you get more familiar with the new SMP-FT feature when you are ready to give it a real spin on real hardware 🙂

Note: Intel Sandy Bridge is recommended when using SMP-FT (real physical hardware) but if you have older CPUs, you enable "Legacy FT" mode by adding the following VM Advanced Setting "vm.uselegacyft" to the VM you are enabling FT on.

One thought on “How to configure SMP-FT using Nested ESXi in vSphere 6?

  1. Hello William,
    I am trying to test FT on nested ESXi v6.5 , VCSA 6.5, both running on pESXi v5.5, vsphere server v 5.5.Following your instructions in the post above, I can enable FT on virtual machine but when I try to start I have following message :
    The available Memory resources in the parent resource pool are insufficient for the operation.
    FT VM has 1GB ram and In cluster I have 11.75 Gb RAM free…
    Another message that I get is that there is no HA resources for VM failover when I try to start VM.
    I tried with Dummy, 32Mb ram VM but still same error messages on power up…

Thanks for the comment!