WHM/CPanel DNS Cluster
​cPanel cluster How it helps your webhosting business



What is cPanel DNS cluster?

A cPanel DNS cluster is a cluster solution offered by cPanel. It consists of one or more nameservers that share DNS records.
By physically separating your DNS service from other services, a DNS cluster helps to keep DNS functionality intact in the event of a server downtime, such as a power outage.
This way, visitors can reach websites on your server more quickly after the web server comes back online.

5 major benefits of having a cPanel DNS cluster

If you are a web host with more than one server and customers hosted globally, well see how you benefit by having a cPanel DNS cluster for your hosting setup.

1. 0% downtime due to DNS service

DNS is a critical service that determines your website availability. Server downtime can occur unexpectedly, due to hardware issues or other catastrophes.
But with a DNS cluster setup, if one of the DNS servers goes down, the other servers in the cluster take up its role and serve the DNS for the website. This will help achieve high website uptime.

2. Faster loading of websites

Website speed plays a major role in online businesses. No customer is ready to wait for ages for your site to load. Thats when a cPanel DNS cluster benefits you.
To ensure that your website loads fast to customers around the world, you can have servers hosted in different locations and use the DNS cluster feature.
Geographical distribution of DNS servers not only reduces the latency involved in processing DNS queries, it also helps to share the load among multiple DNS servers and thus make sites load faster.

3. No loss of emails during server down

Servers can go down unexpectedly, or may need reboots for maintenance. If someone sends a mail to a domain in the server when it is down, they will get a delivery failure message and the mail will not be sent again.
This is because the sending mail server assumes that the domain does not exist. But if a DNS cluster is setup, the sending server will only assume the mail server is down, and holds the mail in queue to retry.

4. Easy domain transfer

A major hurdle involved in domain migrations is the nameserver updates that tag along. With cPanel DNS cluster setup, it is easy to transfer domains among servers.
After migration, 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.

5. Global nameserver setup

With a cPanel DNS cluster, you can use global nameservers for multiple servers. There is no need to maintain separate nameservers for each server.
This system enables server owners to easily update servers every time a change in data has occurred, which makes it easier to keep track of things.
How to setup cPanel DNS cluster

For web servers that have WHM/cPanel, setting up a DNS cluster can be easily done from the WHM. In the dedicated nameservers that are part of the cluster, we install cPanel DNSONLY control panel.



cPanel DNS cluster


DNS cluster is then configured to include these DNS servers. For getting the optimal performance out of the cluster, we perform additional tweaks and configuration settings in them.

cPanel DNS cluster A few hiccups we tackle

Myth of zero downtime

People usually relate clusters to zero downtime. But this does not hold right in the case of cPanel DNS cluster.
A cPanel DNS cluster alone cannot guarantee a 100% website uptime as it is only for DNS service. If the web server itself is down, the site will not load.
For customers who aim for that 99.99% uptime for all services, we configure custom High availability infrastructure with fail over setup for web server, database server, etc.

Performance issues

cPanel DNS cluster can incur slight performance issues due to the latency involved in the DNS record syncs.
At Bobcares, we configure DNS clustering together with Load balancing to overcome these performance issues. This custom setup enables us to provide fast performing servers with absolutely no downtime at all.

Connectivity between servers

In a DNS cluster, connectivity between the DNS servers is crucial.This is usually setup using access keys.
However, firewall rules or change in security policies can affect the connectivity between servers, leading to intermittent errors during DNS zone additions.
To avoid such issues from happening, we perform firewall tweaks and conduct periodic security audits in the cluster to ensure the smooth functioning of the tasks.

Conclusion

cPanel DNS cluster provides an easy way to ensure high uptime for DNS services. But that is not enough to make your site to have zero downtime. Today weve seen how our Support Engineers setup clusters to ensure high availability for websites.

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Many see cPanel multi server (aka cPanel cluster) as a way to prevent business downtime. The logic goes that even if one server fails, the other servers can keep websites and mail online. But, how true is that?In our role as Hosting support specialists for web hosting companies, Our engineers manage hundreds of cPanel servers. We setup and manage several cPanel cluster infrastructure as a part of this cPanel server management services.
From this experience, we could see that though cPanel clusters cannot totally prevent a business downtime, they be used to minimize the impact of a downtime, and to simplify server administration.


cPanel multi-server cluster Do you need it?

As of version 11.56, cPanel offers DNS Cluster for DNS high availability and Configuration Cluster for easier server management. If you already have cPanel servers, heres how cPanel
clusters can help you:


1. DNS cluster How we configure them to prevent service downtime

cPanel creates 2 name servers for each website created in a server (say, ns1.website.com and ns2.website.com). By default, both these two name servers are created in the same physical machine.This poses a couple of issues:

  • In the event of a server crash, DNS will stop working. This brings down both website and mail even if the mail is hosted elsewhere (like Google Apps).
  • If a website needs to be moved to another server due to resource constraints or other reasons, the name servers need to be changed, leading to extensive downtime.


To prevent such downtime, we setup central DNS clusters for our customers. The DNS of all websites would be hosted in 2 or more dedicated DNS servers.This way every website will have the same set of name servers (eg., ns1.webhostingcompany.com, ns2.webhostingcompany.com), and even if one server fails, other servers will ensure that the services are up.With these DNS clusters, weve been able to:


  • Prevent mail bounces using a secondary MX entry for domains, that routes mails to a backup mail server.
  • Avoid web or mail downtime during website migrations to other servers. Since name servers are the same for all domains, theres no need for complex DNS changes and prevents associated downtime.
  • Reduce customer complaints and support tickets that happen during domain migrations.


Many of the name server clusters weve implemented were based on open source BIND servers. cPanel has a similar solution called DNSONLY. With this, cPanel servers can be setup to store DNS records in a remote DNSONLY cluster.When we setup DNSONLY clusters, we maximize the cluster effectiveness and security by:

  • Setting up the name servers in separate geographical locations This ensures that a network issue wont bring down both servers.
  • Making all name servers masters This helps to lower DNS update delays. When a DNS record changes, all name servers in the cluster are updated at the same time. This avoids propagation delay among name servers.
  • Securing the cluster against cache poisoning, and other attacks An attack on the cluster can bring down all websites. We prevent it through a series of DNS security tweaks.




2. Configuration clusters How we use them to simplify server updates

New security threats emerge every day. Servers should be patched and updated frequently to prevent security issues. When you have multiple servers, logging into each of them and running updates can get pretty tiring, and its easy to miss updates.In our role as Server Specialists for small to large web hosting companies, our engineers monitor all security alerts, keep track of server updates, test them for software conflicts, and apply them as soon as possible.While manual updates minimize chances of error, there are a few situations where we perform mass server updates:

  • When widespread hacks are reported via a web app or system vulnerability, patches need to be applied ASAP. There isnt enough time to login to each server and manually do the updates.
  • High priority security channel patches are best applied automatically as they do not conflict with functions.
  • Anti-malware, anti-spam and firewall databases need to be updated as soon as they are available, so as to minimize security issues.

We configure configuration management tools such as Ansible and Puppet to initiate emergency system updates from a central server. This way, we patch all servers in as little as 5 minutes, during a security emergency.

For managed VPS hosting providers, we use a variant of this setup, where regular system updates (eg. RPM updates, kernel updates, etc.) are applied in hundreds of servers using a central control server. This helps us to spend valuable time on other critical tasks.However, if adequate precautions are not taken, such mass updates can lead to software conflicts. To prevent such issues, we ensure these pre-conditions are met, before doing the updates:

  • All VPS instances are ensured to be of the exact same configuration (i.e. same OS, web server, mail server, etc.)
  • Users are not allowed to install server applications, which could conflict with or break the server configuration.
  • Update commands are performed only after conducting a series of tests and ensuring that they are passed.
  • Post update, we run a series to tests from the control server to make sure all VPSs work fine, and all sites load without errors.


[ Focus on your core business without interruptions. Our tech support experts are here to manage your customers 24/7. ]cPanel provides a similar functionality by its configuration cluster solution. With it, you can setup one server as the master, and then ask other servers to use the same Update Preferences as the master server.So, if you setup the master server to Auto-update Apache, all other servers will do the same. The cluster can be setup in the master server by going to WHM Home >> Clusters >> Configuration Cluster. Here, click on the Create button to add the IP, and Remote Access Key to all your cPanel servers (you can get the key from Clusters >> Remote Access Key of the other servers). Itll look like this:

To finish up, go to WHM Home >> Server Configuration >> Update Preferences, and right at the bottom, enable the option Send my settings to all configuration cluster servers. Now, any change you make to the update preferences will be made in all component servers.



Conclusion

cPanel provides DNS clusters for DNS high availability and configuration clusters to simplify server administration. While these do not provide high availability for web and database services, it can be configured to soften the impact of a downtime.At BMITC, we use cPanel clusters and several other methods to deliver high availability and secure server management. To know how these systems can be best adapted for your business

:
https://support.cpanel.net/hc/en-us/...-Cluster-Guide
https://www.interserver.net/tips/kb/...ter-on-cpanel/
https://bobcares.com/blog/cpanel-dns-cluster/
https://binhminhitc.com/how-to/cpane...ting-business/