The vSAN on-disk format version will not update after host upgrades

Products

• VMware vSAN

Issue/Introduction

In a vSAN 2-node stretched cluster, the vSAN data nodes were upgraded and the on-disk format version will not upgrade to the appropriate version.

Environment

VMware vSAN (All Versions)

Cause

 In a stretched cluster, the witness host must also be upgraded in order to update the on-disk format version.

Resolution

In a 2-node stretched cluster with a shared witness, sometimes there may be clusters where the hosts cannot be upgraded due to compatibility or other requirements.  In these cases, it is advisable to deploy a secondary witness appliance.  Clusters that must remain on the older ESXi version can use the witness on that version.  Clusters that can be upgraded can connect the stretch cluster using the upgraded witness.