Backup of vCenter Server depends on which deployment strategy was undertaken. If the vCenter Server is a physical system, then the method used will be different than if vCenter Server is deployed as an appliance.
The recommended practice is to take a full backup of your vCenter Server system. Keep in mind that VMware does not support installing third-party backup agents, so you will need to use a backup product that supports agentless VM backup. A very common practice is to use the VMware Data Protection Appliance or any other products that also use the vStorage API for Data Protection (VADP).
Before starting a conventional backup, the following services should be stopped: