This article explains the Online Health - vSAN Advanced Configuration Check for Urgent vSAN ESA Patch check in the vSAN Health Service and provides details on why it might report a warning.

vSAN ESA clusters running on vSphere 8.0 P02 or higher version, will see this online health alarm as seen below if a specific advance configuration value is not set on all hosts in the cluster.

The issue has been identified that a configuration parameter value was inadvertently changed on vSphere 8.0 P02, this can lead to a mismatch in this configuration value during upgrade from vSphere 8.0 P02 to newer release and hosts may experience PSODs.

Q: What does the Online Health - vSAN Advanced Configuration Check for Urgent vSAN ESA Patch check do?

This check verifies if the advanced config option /VSAN/zDOMOverwriteMiddleMapExtent has been set on all hosts.

Q: What does it mean when it is in a warning state?

If the vSAN advanced config option /VSAN/zDOMOverwriteMiddleMapExtent is not set properly on all hosts, it may impact the cluster upgrade to a higher version and also normal operations of the cluster. It is strongly recommended to resolve the alert by following the troubleshooting guide.

Q: How does one troubleshoot and fix the warning state?

• Open an SSH session and prepare the command  esxcfg-advcfg -s 1 /VSAN/zDOMOverwriteMiddleMapExtent ; auto-backup.sh on all ESX hosts but do not execute it.
• Execute the command in quick succession on all hosts.