Restoring a vCenter Server instance from a backup might impact the clusters in your environment in a seemingly unexpected way. Whether you use images or baselines to manage your clusters, vSphere Lifecycle Manager behaves in a specific manner during backup and restore operations.
When you back up a vCenter Server instance, you create a backup copy of all clusters in that vCenter Server instance.
Restoring vCenter Server After Switching from Baselines to Images for Cluster Lifecycle Management
Cluster A is a cluster that you manage by using baselines. You back up the vCenter Server instance where the cluster is. After the backup, you switch from using baselines to using images to manage cluster A and you remediate the cluster to apply the image to the hosts in the cluster. You now manage the lifecycle of cluster A by using a single cluster image.
If for some reason you must restore the vCenter Server instance from the backup copy you created, the restored vCenter Server instance contains cluster A. Because cluster A was managed through baselines at the time when you backed up the vCenter Server system, the restored vCenter Server instance contains cluster A, but you must again use baselines to manage it.
Restoring vCenter Server After Remediating a Cluster Managed by an Image
After remediation, cluster A uses image X with components Y to manage all hosts in the cluster collectively. At a point in time T, you back up the vCenter Server system. Later, you remediate the cluster against a new image X+1 with new components Y+1. Now all hosts in the cluster use image X+1 with components Y+1.
If for some reason you must restore the vCenter Server system from the backup copy that you created at time T, the restored vCenter Server instance contains cluster A, but the compliance check lists the hosts in the cluster as incompatible with the image that cluster A uses. The reason for the incompatibility is that after the restore operation, cluster A reverts back to using image X with components Y, while the hosts in the cluster still run image X+1 with components Y+1. Because you cannot downgrade ESXi, to make the hosts compliant with the cluster image, you must upgrade the cluster to image X+1 with components Y+1.