I have had various people asking, and to me it felt like an obvious answer, but as multiple have asked over the past couple of month I figured I would dedicate a post to it. The question is if it is supported to run the vSAN Witness Appliance for a 2 Node vSAN configuration on the 2 Node vSAN Configuration itself, but then with vSphere SMP-FT enabled on the Witness for extra protection.
The short answer: No, this is not supported.
The slightly longer answer: No, this is not supported. The vSAN Witness needs to run outside of the vSAN cluster it is acting as a witness for. The reason for this is fairly straight forward: Just imagine the vSAN hosts are partitioned and cannot talk to each other, yet both may have access to the Witness as a result of FT doing what it is designed to do. But those are different instances of the same Witness, which potentially can lead to all sorts of strange problems.
Hi Duncan.
Is it supported to run the witness appliance in Cloud? I see that there’s a doc about Running VMware vSAN Witness Appliance in VMware vCloud Air but what about others clouds ?
Thanks
M
Yes that is supported
Hi Duncan,
Is it possible to run a 3 node vsan cluster with a witness appliance on a separate non vsan local cluster? The goal would be to maintain FTT=1, while one host is put into maintenance mode. The alternative of purchasing a 4th node for the vsan is a substantial financial increase in the deployment.
Regards,
Paul
In the described scenario is it not possible that even if the Witness VM is in a third physical location, both hosts may have access to it, even thought they’ve lost connection with each other?