Premium DNS accounts offer a higher level of support and advanced features to add power, flexibility, and control to your DNS management:
To upgrade to Premium DNS, see Upgrade to Premium DNS.
Secondary DNS provides redundancy for your primary nameservers. If something goes wrong with your primary (and only) nameserver set, you run the risk of requests hitting a dead end with nowhere else to go. You can back up your DNS zones with Secondary DNS (a secondary nameserver) so your domain name never goes offline.
If you manage your own nameservers and want redundancy or a backup, you can enable this advanced feature in your Premium DNS account. For more information, see What is Secondary DNS?.