vCenter Upgrade from 8u3X to 9.0.X fails with at "VCENTER UPGRADE PRECHECK" phase

Products

• VCF Operations

Issue/Introduction

In a Brownfield VCF Imported scenario, see documentation, a vCenter upgrade from vCenter 8UX to 9.0.X can fail at the "VCENTER UPGRADE PRECHECK" Phase.





SDDC manager logs state the following

SDDC manager 

less -i lcm-debug.log
<date && Time> DEBUG [vcf_lcm,69974c401d3fdcbf68da4526ad82674a,c48e] [c.v.evo.sddc.lcm.model.task.Stage,http-nio-127.0.0.1-7400-exec-6] Stage details: Stage(id=6:3, name=null, description=null, type=VCENTER_UPGRADE_PRECHECK, order=3, startTime=null, endTime=null, duration=null, status=FAILED, errorType=null, errorCode=null, errorDescription=null, remediation=null, resources=null, errors=null, notifications=[Notification(severity=ERROR, stage=VCENTER_UPGRADE_PRECHECK, timestamp=1771523088527, message=LocalizableMessageid=vcenter.deployment.migration_upgrade.auto_population_error, defaultMessage=The values for appliance size and disk size parameter could not be determined automatically. Please provide the parameter manually to proceed further. Check logs for more details, messageAttributes={0=[]}, localized Message=The values for appliance size and disk size parameter could not be determined automatically. Please provide the parameter manually to proceed further. 
Check logs for more details, version=null), originator=vCenter, errorType=RECOVERABLE, remediationActions=null, referenceToken=MN84IB), Notification(severity=INFO, stage=VCENTER_UPGRADE_PRECHECK, timestamp=1771523089650, message=LocalizableMessage(id=b09f9ed
7-2e89-4ff7-8e53-552a81f2e25a, defaultMessage=vCenter upgrade is rolled back., messageAttributes=null, localizedMessage=vCenter upgrade is rolled back., version=null), originator=VCF LCM Service, errorType=RECOVERABLE, remediationActions=[LocalizableMessage(id=a9deb6b5-6a40-4ea5-ba33-1fef8fb5e371, defaultMessage=Please retry the upgrade. Contact GSS for assistance, if the retry fails., messageAttributes=null, localizedMessage=Please retry the upgrade.

Environment

vSphere 9, brownfield import .

Cause

The SDDC to vCenter API fails to determine the appropriate size of the target Appliance.
In vSphere 9.X we use the RDU process, so we can't manually select an appropriate size, for the said target appliance.
Cause is the allotted RAM value, which was over 58GB which is the XL size - https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/8-0/vcenter-installation-and-setup/deploying-the-vcenter-server-appliance/vcenter-server-appliance-requirements.html 

Resolution

Need to revert back to default size/ lower then XL maximum.

1. Make sure backup and snapshot is available 
2. Revert back to the Default value of the vCenter template, or a value that's lower then 58 GBs
3. Retry the process
4. RDU should deploy/ upgrade the VCSA Appliance. 

Documentation below 
https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/8-0/vcenter-installation-and-setup/deploying-the-vcenter-server-appliance/vcenter-server-appliance-requirements.html