vCenter Server can be backed up using two methods today; image-based (VM backup) and file-based backup built into the vCenter Server itself.
In this blog, we will answer the question; why use file-based backups versus image-based backups when it comes to vCenter Server?
The short answer is; because of SSO domain data.
When you have multiple vCenter Server instances in a single SSO domain, participating in Enhanced Linked Mode (ELM), you have data replicating between each instance. When you take a backup of a vCenter Server instance, it is a snapshot in time. The state of the vCenter Server and its data, at that moment. In the event that you restore a vCenter Server from backup, it’s akin to sending that instance back-in-time, while the other members of the SSO domain are still in the present. This can lead to SSO domain data conflicts.
File-based restores handle this back-in-time situation by authenticating with the SSO domain and reconciling the SSO domain data during restoration. The restoring vCenter Server will be restored to the SSO domain without conflicts. When using image-based backup and restore methods, this reconciliation cannot happen.
During a file-based restoration, you are prompted for the SSO administrator credentials. This allows the restoring vCenter Server to correctly synchronize with the current state of the running SSO domain.
When is it ok to use image-based backups?
If you have a standalone vCenter Server instances, not participating in ELM, then using image-based backup solutions should have no issues. If you have vCenter Server instances participating in ELM then you should avoid using image-based backup solutions and use only the native file-based backup feature of the vCenter Server.
Important: When restoring from file-based backup, you must use the same build of vCenter Server installation media that corresponds with the vCenter Server build of the backed up instance. For example, if you have backed up a vCenter Server version 7.0 U3d, then you must use the version 7.0 U3d installation media to restore.
It is recommended to take frequent backups of all vCenter Server instances. The native file-based backup feature of the vCenter Server can schedule automatic backups to occur daily, weekly, or on a custom cadence. You can also configure the number of backs retained by each instance. If a scheduled backup fails, an alarm will be triggered in the vSphere Client to notify you.
Testing vCenter Server Backups
It is important to regularly validate the integrity of vCenter Server backups and ensure that they can be restored successfully. You can test vCenter Backups by restoring them to an isolated network to avoid conflicting with running production instances. The last situation you want to find yourself in, during a scenario where you need to restore from backup, is that the backups you have are not valid.
Important: When using vSphere Distributed Switch port groups for the vCenter Server network, make sure the port group is configured as ephemeral. When restoring a vCenter Server instance, using ESXi as the deployment target in the case of a self-managed vCenter Server, the restore wizard will be unable to see non-ephemeral port groups.