Backing up the vCenter Server Appliance (VCSA) is an important step in ensuring that your virtual infrastructure is protected against data loss or corruption. There are several methods available for backing up the VCSA, but not all of them are equally effective or recommended.

One method that is often used to back up the VCSA is to use a backup application like VM Backup, while this may seem like an easy and convenient option, it is actually not recommended for several reasons.

First, taking snapshots of the VCSA can cause performance degradation and instability. Because the VCSA is a critical component of your virtual infrastructure, any performance issues or instability can have a major impact on the overall health and availability of your environment.

When a backup application tries to take a snapshot of the VCSA, the vCenter server is temporarily disconnected from the vSphere environment. This can cause issues with other applications that rely on the vCenter server, such as virtual machines that are in the process of being migrated or managed by the vCenter server.

Additionally, snapshot-based backups are not a complete or reliable way to back up the VCSA. Snapshots only capture a point-in-time view of the system, and do not include all of the data and configurations that are necessary to fully restore the VCSA. This means that in the event of a disaster, you may not be able to recover all of your data or restore the VCSA to its previous state.

The recommended method for backing up the VCSA is to use the built-in backup and restore functionality provided by the appliance itself. This method allows you to create complete and consistent backups of the VCSA, including all of the necessary data and configurations.

The above is also mentioned in VMware's vCenter Server Appliance Data Integrity Best Practices KB.

To backup the VCSA using this method, follow these steps:

1. Log in to the VCSA management interface.
2. Navigate to the "Backup" section in the "Administration" tab.
3. Select "Schedule a New Backup" and configure the backup settings as desired.
4. Click "OK" to start the backup process.

More detailed steps provided by VMware, here.

Once the backup is complete, you can restore the VCSA by following these steps:

1. Boot the VCSA from the ISO file or bootable media.
2. Select the "Restore" option from the main menu.
3. Follow the on-screen instructions to restore the VCSA from the backup file.
4. After the restore is complete, restart the VCSA and verify that it is functioning correctly.

More detailed steps provided by VMware, here.