The OS / boot drive is a quickly replaceable item as long as you have a current configuration file. If you really want to you can do a 2 way mirror.
You can do a new install of your current OS on the boot drive and upload the configuration file and be back to 100%. Mirroring the boot drives is usually when you need to be up quickly with a boot drive failure and you have someone to change the boot order to the second drive. It’s more for SMB or Enterprise.
