The VCSA Installation wizard incorrectly detects the storage deployment size of the source vCenter during migration or upgrade

Products

• VMware vCenter Server

Issue/Introduction

When attempting to upgrade vCenter Server from versions 6.5 or 6.7 to 7.x, 8.x or from 7.x or 8.x to 9.x, the upgrade wizard may incorrectly detect the storage deployment size for the source vCenter Server.

For instance:

• A source vCenter Server originally deployed with a "Normal" storage size might only present "Large" or "X-Large" as available storage size options during the upgrade.
• Similarly, a source vCenter Server deployed with a "Large" storage size might find that only the "X-Large" storage configuration is available in the installer.
• Due to this behavior, the error "Insufficient disk space on datastore" may appear during the upgrade if the datastore where the vCenter is being deployed does not have enough free space to accommodate the selected storage size.

Environment

• VMware vCenter Server 9.X
• VMware vCenter Server 8.x
• VMware vCenter Server 7.x
• VMware vCenter Server 6.x

Cause

This behavior can occur under the following conditions:

• vSAN Datastore Provisioned Space

  • The source vCenter Server is deployed on a vSAN datastore with a Failure To Tolerate (FTT) value set to 1 or higher.
    
    
  • The VCSA installer utilizes the provisioned space of the VM to determine the storage size during deployment.
    
    
  • On a vSAN datastore, the provisioned space of the VM includes the capacity consumed by its mirroring/RAID components (due to FTT). This can result in the provisioned space appearing significantly larger than the VCSA VM's actual used space.
    
    
  • Example: 173GB of used space would result in 346GB of provisioned space for a VCSA VM with an FTT=1 (Mirror) vSAN storage policy.
    
    
  • If the calculated provisioned space exceeds the "Default" storage size for the selected VCSA size, only the next larger storage options will be displayed in the dropdown menu.

• High Disk Utilization on Source Appliance

  • More than 50% of the space available in either the /storage/seat, /storage/db, or /storage/updatemgr partitions is in use on the source vCenter Server Appliance.
    
    
  • To verify disk utilization, SSH into the vCenter Server Appliance and execute:
    
    df -h

• The provisioned space of the source vCenter Server is larger than the target storage size

  • The upgrade wizard shows that the source machine's storage size is larger than the destination's.

Note: The source machine size refers to the provisioned size, which includes not only virtual disks but also swap files, log files, and snapshot files.

Resolution

Note: While there are articles available on the Internet describing how to shrink the disks of the VCSA after you finished the upgrade, be aware that none of them are officially supported.

Instead, follow the below two-stage approach during upgrade: 

Stage 1

1. Open the VCSA installation wizard
2. Instead of "Upgrade", select the "Install" Option
3. In "Select deployment size," choose "Small" or "Medium" as the "Deployment size", similar to how the source vCenter Server was deployed. Notice that the "Storage Size" field is set to "Default"
4. When configuring the network settings, be sure to set the IP as the temporary IP designated for the upgrade process.
5. Finish Stage 1 by providing other details. (Note: Node type (embedded/external PSC, etc.) has to be same as the source VC.)
6. Notate the IP of the appliance and exit the installer.

Stage 2

1. Open the VAMI UI webpage:
   https://<New_APPLIANCE_IP>:5480
2. Login using the root credentials used in Stage 1.
3. Select the "Upgrade" option.
4. Provide the source (old) vCenter details using the IP of source vCenter instead of the FQDN because it may not resolve on the network and the FQDN will be pointing to the source vCenter.
5. Provide the information required by the upgrade wizard.
6. Start the upgrade process.

After the upgrade is complete, connect to the appliance and confirm all previous settings are in-place.

Additional Information

Note: Downsizing VCSA during Upgrade

This approach can also be utilized to downsize a vCenter Server Appliance (VCSA) during an upgrade. For instance, if the original VCSA was deployed with an "X-Large" storage configuration, but the target VCSA requires only a "Large" or "Normal" storage size, this method is applicable. However, it is crucial to ensure that the new VCSA possesses sufficient storage capacity to successfully accommodate the data imported from the source appliance.

Also see: System Requirements for the vCenter Server Appliance