Disk group unhealthy after adding disk previously used in another vSAN cluster

Products

• VMware vSAN 7.x
• VMware vSAN 8.x

Issue/Introduction

Symptoms: 

• Disk group shows as unhealthy in Cluster -> Configure Tab -> Disk Management: 

• Disk appears in a new disk group without having added it, along with an absent cache disk that had not previously existed: 

• The disk does not appear in the "Ineligible and Unclaimed"  section in Cluster -> Configure Tab -> Disk Management.

Environment

• VMware vSAN 7.x
• VMware vSAN 8.x

Cause

• vSAN will try to automatically mount a vSAN disk that appears to have valid vSAN partition on it, so will not be eligible to be claimed for a new or existing disk group. 

Resolution

Follow these steps to resolve this issue: 

1. Remove the disk from vSAN disk group.  See KB: How to remove a disk from a vSAN disk group/host
2. Erase the partitions on the disk. See TechDocs: Erase ESXi Storage Devices
   • CAUTION:  Ensure the data on the disk is not longer needed before erasing the partitions.
3. Add the disk to new or existing disk groups, as needed.   See TechDocs:  Add Devices to the Disk Group in vSAN Cluster and Create a Disk Group or Storage Pool in vSAN Cluster