If you go by best practices the best practice is to keep your vCenter server on a VM. Which will serve the purpose incase of host down where vCenter HA will take care in the event of failure. This solves half of the purpose to secure vCenter server (or vCenter DB) as these are on virtual machine.
Considering your case where you have single Physical vCenter Server ideal scenario will be to have 2 vCenter DB server
Please check the link if it helps you How to install and configure highly available (cluster) VMware vCenter on WSFC? | Settlersoman - A settler in the SDDC w…