Error: "Applying personality to cluster failed" during VCF Stretched Cluster Creation due to vSAN MTU Health Check

Products

VMware SDDC Manager / VCF Installer

Issue/Introduction

During the creation of a vSAN Stretched Cluster for Management domain via VMware Cloud Foundation (VCF) Operations, the workflow fails.

The workflow fails during the Stretch vSAN Cluster operation sequence, specifically halting at the Remediate ESXi Host(s) to be Compliant with Cluster's Image subtask with the following error output:

Description: Remediate ESXi Host(s) to be Compliant with Cluster's Image
Progress Messages: Applying personality to cluster domain-c# failed with error: com.vmware.vapi.std.errors.Error: Error (com.vmware.vapi.std.errors.error) => { messages = [LocalizableMessage (com.vmware.vapi.std.localizable_message) => { id = com.vmware.vcIntegrity.lifecycle.TaskError.HealthCheckFailed, defaultMessage = Health Check for '####' failed, args = [####], params = <null>, localized = Health Check for '####' failed }], data = <null>, errorType = ERROR }

vCenter Server UI displays the following error under the Remediate Cluster task:

A general system error occurred:&amp;#10;&amp;#34;Health Check for #### failed&amp;#34;

Navigating to Cluster > Monitor > vSAN > vSAN Health reveals an active, unsilenced warning for:
```
vSAN: MTU check (ping with large packet size)
```

The SDDC domain manager logs (/var/log/vmware/vcf/domainmanager/domainmanager.log) report the following exception:

ERROR [vcf_dm,...] [c.v.e.s.o.model.error.ErrorFactory,dm-exec-722]  [EO331] VLCM_REMEDIATE_PERSONALITY_FAILED Applying personality to cluster domain-c# failed with error: com.vmware.vapi.std.errors.Error: Error (com.vmware.vapi.std.errors.error) => {
    messages = [LocalizableMessage (com.vmware.vapi.std.localizable_message) => {
    id = com.vmware.vcIntegrity.lifecycle.TaskError.HealthCheckFailed,
    defaultMessage = Health Check for '####' failed,
    args = [####],
    params = <null>,
    localized = Health Check for '####' failed
}],

INFO "id":{"value":"com.vmware.vcIntegrity.lifecycle.health.common.overall_health_not_green"},"originator":{"value":{"value":"vSAN"}},"message":{"fields":{"args":{"list":[{"value":"vSAN: MTU check (ping with large packet size)"},{"value":"####"},{"value":"vSAN reports this issue when the large ping (9000 bytes packet size) pass rate is less than 30% for vSAN network among ESXi host."}]},"localized":{"value":{"value":"vSAN health test 'vSAN: MTU check (ping with large packet size)' reported an issue for cluster '####'. Detailed error message: vSAN reports this issue when the large ping (9000 bytes packet size) pass rate is less than 30% for vSAN network among ESXi host."}}

The vCenter Update Manager logs (/var/log/vmware/vmware-updatemgr/vum-server/vmware-vum-server.log) records the below errors:

INFO vmware-vum-server [vc@#### sub="Telemetry"] [TelemetryManager 278] Sending telemetry data: {"@type":"pman_error_report","taskId":"####|####","entityId":"####|host-####","parentTaskId":"","errorMessageId":"com.vmware.vcIntegrity.lifecycle.health.common.overall_health_not_green","errorMessage":"vSAN health test 'vSAN: MTU check (ping with large packet size)' reported an issue for cluster '####'. Detailed error message: vSAN reports this issue when the large ping (9000 bytes packet size) pass rate is less than 30% for vSAN network among ESXi host.","errorTime":"####"}

ERROR vmware-vum-server [vc@#### sub="RemediateClusterTask"] [Task, ###] Task:com.vmware.vcIntegrity.lifecycle.RemediateClusterTask ID:####. Task Failed. Error: Error:
-->    com.vmware.vapi.std.errors.error
--> Messages:
-->    com.vmware.vcIntegrity.lifecycle.TaskError.HealthCheckFailed<Health Check for '####' failed>

INFO vmware-vum-server [vc@#### sub="PM.AsyncTask.RemediateClusterTask{42}"] [vciTaskBase 1493] SerializeToVimFault fault:
--> (vmodl.fault.SystemError) {
-->    faultCause = (vmodl.MethodFault) null,
-->    faultMessage = (vmodl.LocalizableMessage) [
-->       (vmodl.LocalizableMessage) {
-->          key = "com.vmware.vcIntegrity.lifecycle.TaskError.HealthCheckFailed",

Cause

This is expected behavior caused by the strict prerequisites of vSphere Lifecycle Manager (vLCM). vLCM requires the target cluster's overall vSAN health state to be 100% healthy ("Green") before it allows remediation or stretching operations to proceed.

The vSAN MTU health check uses large packets that drop over the standard MTU 1500 WAN link to the Witness Appliance. This triggers a health alert (overall_health_not_green), causing vLCM to safely abort the remediation. This is expected behavior (see vSAN: MTU check (ping with large packet size)).

Resolution

To unblock the deployment immediately, temporarily silence the vSAN MTU alert so that vCenter Server reports a healthy vSAN state.

Step 1: Silence the vSAN MTU Health Check Alert

Log in to the vSphere Client and navigate to the target cluster.
Go to Monitor > vSAN > vSAN Health.
Expand the Unhealthy warning for vSAN: MTU check (ping with large packet size).
Select the alert and click Silence Alert. KB: Silencing a vSAN health check
Wait a few moments and verify the overall vSAN cluster health now reports as Healthy (Green).

Step 2: Resume the Deployment

Return to the VCF Operations UI.
Restart the failed Stretched Cluster creation task.
The vCenter Remediate Cluster subtask will now pass the vLCM pre-checks, and the deployment will complete successfully.
(Note: Once the stretched cluster deployment is fully completed, the vSAN MTU alert can be unsilenced if required by your organization's monitoring and compliance policies).