Understanding cPanel clustered DNS and Setup

What is DNS and why do we care?

DNS is the service that resolves domain names like sysadminspot.com to IP addresses. So instead of memorising all the possible IP addresses in the world and who they belong to, we use domain names (example.com). DNS resolution takes place on a DNS server. The server takes the domain name given to it and looks to see if it has an IP address for it. If it doesn’t, it may forward to it another DNS server. So if your memory is like mine, then you care about DNS.

Why cluster DNS?

Well firstly it sounds really cool, however increased performance is also another key factor.

Explain how said performance increase would work…

As mentioned before, DNS resolves domain names (sysadminspot.com) to an IP address. This is one step in a bucket full of steps when it comes to loading a website. But if just one fails or is slow – websites don’t load!

Here’s an example:

You have three servers running in the United States. However your customers and their visitors are geographically scattered.  Customers in the UK and Australia often complain that their websites load slowly but they load really quickly for you in the United States.

This is because of network latency. It generally takes longer to talk to a network that is cross continental than one in the same country as you. Same applies if you wanted to go shopping and went to Europe instead of down the road – it’s gonna take longer!

How about this though:

  1. You deploy several virtual servers (low cost) in key geographic locations around the world (e.g. Sydney and London).
  2. You install cPanel DNS Only
  3. All your servers are configured to synchronise DNS with the new DNS servers.

So what has changed? Well now your customers in Europe are talking with the DNS server in London instead of the United States. One way communication drops from 300ms to 150ms and hence, resolution takes place faster. Yes, it is certainly the case that now that customer now has to go back to talking with the US server to grab the files. But you’ve collectively saved a lot time for all your customers.

You can also distribute some of your server load to other servers. Let your web and database servers focus on serving dynamic page content. Outsource your DNS to distributed, cheaper and less busy servers. You’ll save bandwidth, reduce congestion and lower disk I/O.

Redundancy… sounds cool right?

After a scheduled reboot your DNS service doesn’t start. Under standalone DNS circumstances, domain names cannot be resolved to IP addresses and therefore websites are down.

However with the clustered DNS setup customers just attempt to connect to another server, even if it’s in another country. This isn’t something you need to setup either, it’s build into the standards and protocols of DNS.

Okay, I want it, give it to me! How do I set it up?

Yes that’s what I thought. Check out the cPanel documentation below which includes all the sexy looking screenshots you could want.

Installation Guide – Install cPanel DNSONLY
cPanel DNSONLY Summary

Let me know if the link stops working. cPanel are constantly breaking their documentation links with redesigns.

EDIT 27 Dec 2015: Thanks Felix for the heads up, links fixed. 🙂

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