vSAN Health Checks

I am a bit new to using vSAN and have a couple questions on the health checks.

One I am getting a warning on the "vSAN Disk Balance" and 2 of my 5 servers, looks like 3 disks from one and 1 from the other, have the "Proactive rebalance is needed". If I use the "Configure Automatic Rebalance" will this affect any of the current data or any issues at all to the the vSAN?

Another health check that is in error state is the "vCenter state is authoritative" with all 5 hosts out of sync. What exactly will happen if I "Update ESXi Configuration", is there a risk to lose any data at all?

Thank you!

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VMware Employee
VMware Employee

@HockeyFan04, Welcome to Communities and vSAN.

vSAN Health alert relating to Disk Balance is basically an informational alert that there is >30% variance between highest and lowest used Capacity-Tier disks in the cluster - vSAN doesn't automate moving data to newly added/blank disks for multiple reasons and thus why Proactive Rebalance exists. If all nodes in the cluster are 6.7 U3 or higher then you can configure this to proactively rebalance automatically, if lower then you can push the button from the Health UI to start this task, this is intentionally very very low priority IO and thus should have no impact on performance (and zero impact on data-state as it is just moving data and only removing the original data it moved once completed).


"vCenter state is authoritative" is a little more complex - this triggers if vCenter has not pushed and/or is not in sync with the unicast agent lists on the nodes (basically the list nodes have to know who is in the cluster) - did you add this cluster to a new or restored from backup vCenter and/or were there any manual changes via the CLI of the unicast agent entries?
First steps should be to validate that no nodes are set to ignore vCenter membership updates:

# esxcfg-advcfg -g /VSAN/IgnoreClusterMemberListupdates
If this is set to 1 then this node is set to ignore vCenter updates, this should by default be set to 0:
# esxcfg-advcfg -s 0 /VSAN/IgnoreClusterMemberListupdates
Next you should validate that the vSphere cluster members match the vSAN cluster members, check the nodes in the vSphere UI vs the members and as per 'esxcli vsan cluster get' - if they match and the above checks and remediation (where necessary) has been done, then you can go ahead and click "Update ESXi Configuration" - either way there is no risk to the data but the above checks need to be performed to avoid any possible cluster partition.