On-disk format upgrade pre-check fails "Hosts are not in given VIrtualCenter cluster were detected to participate in the vSAN cluster"

Products

• VMware vSAN

Issue/Introduction

On-disk format upgrade pre-check from vCenter UI > Cluster > Configure > vSAN > Fault domain is failing with below error.

Hosts <Witness node UUID> are not in given VirtualCenter cluster were detected to participate in the vSAN cluster.

Environment

VMware vSAN 7.x
VMware vSAN 8.x

Cause

The issue occurs when the Witness host is not is not added to the vCenter Server inventory.

In vCenter UI, Cluster > Configure > vSAN > Fault Domains shows the Witness node as 'Out of Inventory Witness'.

Resolution

• Add the Witness node to the vCenter inventory.
• Follow the steps provided in the below article to fix the 'Out of inventory witness'.
  Out of inventory witness alerts seen in vSAN cluster Fault Domains
• Perform the on-disk format upgrade once the 'Out of inventory witness' issue is fixed.