When running a 4 node stretched cluster environment it should be possible to use “cheaper” vCenter Server licenses, namely vCenter Foundation. One of the limitations of vCenter Foundation is that you can only manage 4 hosts with it. This is where some customers who wanted to manage a stretched cluster hit some issues. The issue occurs at the point where you want to add the Witness VM to the inventory. Deploying the VM, of course, works fine, but it becomes problematic when you add the virtual ESXi host (Witness Appliance) to the vCenter Foundation instance as vCenter simply will not allow you to add a 5th host. Yes, this 5th host would be a witness, and will not be running any VMs, and even has a special license. Yet, the “add host” wizard does not differentiate between a regular host and a virtual witness appliance.
Fortunately, there’s a workaround. It is fairly straightforward, and it has to do with the order in which you add hosts to vCenter Foundation. If you add the witness VM before the physical hosts then the appliance is not counted against the license. The license count (and allocation) apparently happens after the host has been added, but somehow vCenter does validate beforehand. I guess we do this to avoid abuse.
So if you have vCenter Foundation, and want to build a stretched cluster leveraging a 2+2+1 configuration, meaning 4 physical hosts and 1 witness VM, then simply add the Witness VM to the inventory as a host first and then add the rest. For those wondering, yes this is documented in the release notes of vSphere 6.5 Update, all the way at the bottom.
https://docs.vmware.com/en/VMware-vSphere/6.5/rn/vsphere-vcenter-server-65u2-release-notes.html#licensing-issues-known
Is the direct link to the vCSF “witness host” issue you’re referring-to.
Hi,
It´s an old post and I hope I still get an answer 🙂 Is it supported to manage a 4-node stretched cluster + Witness appliance with vCenter Foundation or is it just for lab environment?
I tried to add four hosts and the witness host and it works without problems on vSphere 6.7, but if it´s not supported I can´t recommend to my customers. I´m looking forward for your response.
Best regards
Sebastian
I have a second question about the witness appliance 🙂 It is (technical) possible to deploy the virtual Witness appliance on Workstation Player and Workstation pro. Is it supported to do this or is it realy just for testing? This, in combination with supported 4node+virtual Witness appliance on vCenter Foundation, would be an awesome opportunity for us to offer vSAN even for small business.
Best regards
Sebastian
It is not supported on Workstation or Fusion yet. It is supported to go above the Foundation limit. It was a problem previous that is solved in 6.7 u1: https://docs.vmware.com/en/VMware-vSphere/6.7/rn/vsphere-vcenter-server-671-release-notes.html
Thanks for your fast response, maybe it will be supported in future to deploy the virtual witness appliance on workstation (pro) because it is technically possible 🙂 The info with vCenter Foundation is very helpful, thanks for it.
Best regards
Sebastian
If using vSphere Essentials and accidentally added the 3rd host to the cluster before the witness how do you recover from this? I added tried unregistered the 3rd physical host, registering the witness which worked, but receive host limit warning when trying to register the 3rd physical host.