So, do you want to be 100% sure that your domain is online? Backup DNS for your Primary DNS service is a handy addition that will make your DNS network broader. If you use a Backup DNS, you can add multiple nameservers that will be authoritative for your domain and answer queries.
Backup DNS service (Secondary DNS) is an additional DNS service that you can get from another DNS provider, different from your primary, with the goal to add extra redundancy. You can use extra nameservers as authoritative, and they can answer queries too.
If you could have an x-ray of the Internet or any other network, you could see how servers are the keystone for them to work. The amount of them and the tasks they comply with are vital for these systems’ existence.
It’s called Primary DNS server or Master DNS server. These names indicate its importance since it’s the source of all the original data for a specific DNS zone and its corresponding domains. A Primary DNS server is responsible for storing all the DNS records for its DNS zone. Therefore, every time a record (or more) requires a change, edition, or to be deleted, that can only be made in the original source, the Primary DNS server.