The Witness host must not be part of a vSAN enabled Cluster

As part of a vCenter 7 to a brand new vCenter 8 migration, the vSAN clusters had to be moved in addition to the normal clusters.

When we disconnected the vSAN Witness Appliance from the old vCenter in the last process and then wanted to add it to the fault domain in the new one, we were confronted with the following error message:

Although these are the same vSAN data nodes, they are no longer the same cluster IDs, which have been redefined in the new vCenter.

However, the Witness Appliance still has the IDs from the old vCenter. To add the appliance to the new vCenter/cluster, the following steps must be followed – first open a Web Console off the Witness VM and go to Troubleshooting Options:

Then enable ESXi Shell and press ALT + F1 to switch to the CLI:

Now confirm the witness is part of a cluster by running following Command:

esxcli vsan cluster get

As you can see, the Witness appliance sees the two other nodes and the cluster as “complete”, but we still cannot store the Witness in the fault domain due to the different cluster IDs. Therefore we have to leave the Witness Appliance from the vSAN cluster by running follwing command:

esxcli vsan cluster leave

We check one more time whether the Witness is a member of a vSAN cluster:

esxcli vsan cluster get
vSAN Clustering is not enabled on this host

The Witness Appliance is now free of cluster dependencies and can be added to the new cluster as a Witness as usual.

This is it from this Blog post, if you have any questions please use the comment section below. 🙂