After upgrading a vSAN OSA cluster to 9.x, warning 'vSAN is enabled on the cluster without vSAN ESA, but a storage pool is detected on this host.' is displayed in Skyline Health

Products

• VMware vSAN

Issue/Introduction

• vSAN ESA-related warning 'storage pool is detected' is triggered after upgrade to 9.x, despite vSAN OSA being used. 
• SDDC Manager did not detect mixed-use configuration present and allowed the upgrade to complete. 
• After upgrade, manual verification of this issue being present can be confirmed via ESXi shell using:

esxcli vsan storage list

and

esxcli vsan storagepool list

These will confirm that both configurations are present on the hosts: vSAN OSA disk group (claimed, in use) alongside vSAN ESA Storage Pool (unclaimed). 

Environment

VMware vSAN 

Cause

This issue is caused by the presence of unclaimed storage devices, previously configured for vSAN ESA Storage Pool but not wiped after being decommissioned from previous setup. 
At current, SDDC Manager upgrade workflow checks only single (current / vSAN OSA) configuration in use and does not detect alternative (vSAN OSA, unclaimed) configuration present.

Resolution

Manually remove partition from unclaimed devices using Remove Partition From Devices.