Wednesday, September 14, 2011

Benefits of a DNS cluster

A DNS cluster is a number of nameservers that share records. This allows you to physically separate your nameservers, so that in the event of, for instance, a power outage, you still have DNS functionality. This way, visitors can reach websites on your server more quickly after the web server comes back online.
If you are already using WHM/cPanel for your webservers, setting up a DNS cluster is quite simple. For optimal performance, it is recommended to have dedicated DNS servers along with your webservers. So you can install the “cPanel DNSONLY” control panel on those server for easy integration with your current WHM/cPanel servers. You can download it here. The instructions on how to setup the DNS cluster using cPanel are mentioned here

This post is for those readers who mainly need to now the advantages of using a DNS cluster.

1. 0% downtime due to DNS service being down. If the DNS service is down in the server, the domain DNS will be served by the other servers in the cluster.
2. If a server is down (say being rebooted), and at that point if someone tries to send an email to a domain on that server, they will get a delivery failure message and the mail will not be sent again. This is because the senders mail server will assume the domain does not exist. But in case a DNS cluster is setup, the mail server sending the mail will only assume the mail server is down, and hold the mail in its queue to be retried again. No delivery failure report message will be sent.
3. It is easy to transfer domains among servers. The client will not have to change the nameservers used by the domains. The same nameservers can be used to point the domain to the new server.
4. You can use Global nameservers for all your servers. No need to set specific nameservers for each server.

There aren’t many demerits except that there should be a slight affect on the performance, which should be negligible. Also 0% downtime does not stand true, if the webserver is down. Then the site will be down, even if DNS is responding.
DNS clustering together with Load balancing will definitely give you the fastest performing servers with absolutely no downtime at all.

I hope this tutorial will help you achieve faster response times for your sites.