Error: "Invalid cluster size present. VSAN storage cannot be used as primary datastore for cluster" in validation checks for VCF 9.0 using non-VSAN datastores

Products

• VMware vCenter Server
• VMware Cloud Foundation

Issue/Introduction

During a VCF 9.0 deployment where an existing vCenter is converged into the domain, the validation prechecks may show the following two errors: 

Cluster is not vSphere Lifecycle Manager (vLCM) image based

Invalid cluster size present. VSAN storage cannot be used as primary datastore for cluster <NAME>, Cluster <NAME> has size 2 which is unsupported for CONVERT operation

However, the vCenter being converged contains no VSAN datastores. 

Environment

VCF 9.0

Cause

The "VSAN cluster size check" error is triggered as an unexpected side effect of the "LCM check".

Please note that this is only applicable if both of these validation errors exist.

Resolution

Converting the cluster to an LCM-Imaged based cluster will resolve both validation errors.