What is server redundancy?

There are various ways to guard against — and address — IT disasters in your business. You can set up a well-planned downtime communication plan. You can have your IT team implement robust cybersecurity practices. And you can also use something called server redundancy.

Redundancy is not usually a word people associate with good things. But in the IT world, it can mean the difference between your service running, and catastrophic unplanned downtime.

So, what is server redundancy?

Servers and redundancy

Before getting into what server redundancy is, it’s worth defining the two key terms involved.

Server: The hardware that serves data to other computers. When you access a website, data or program over a network, you’re sending a request to a server, which delivers the resource you want.

Redundancy: An engineering term that refers to the creation and maintenance of duplicate critical components or functions of a system. If everything works as it should, these duplicate components are not in active use. (Hence the name ‘redundant’.)

A redundant server, then, is an extra server that is a duplicate of a business’s active one. It is not used as a live server but remains powered on and ready for use when the need arises.

Why have a redundant server?

The goal of server redundancy is to ensure zero downtime for your services and resources. It eliminates single points of failure because it provides a back up to your critical devices and systems.

If something should go wrong with your primary server, the redundant server can take over and continue to serve your users and team members and so on. This is known as a failover procedure.

Redundant servers can also provide support to the primary server in times of unusually high traffic. Too much traffic would normally result in service inaccessibility. But, with a redundant server to take on some of the strain, there’s a better chance of keeping your resources and services accessible.  

The downside of server redundancy

Server redundancy is a particularly useful method for ensuring the reliability of your services and offering. But as with anything, there is a cost.

When it comes to redundant servers, the cost is literal. It takes money and resources to buy a second server, store it, maintain it, and run it. So, when considering server redundancy, it’s worth considering the cost — and the potential price of failure if you don’t have a redundant back up.

You can think of server redundancy as a bit like insurance. You pay for it, and if nothing happens, you didn’t need to pay for it. But if something does happen, that cost expenditure could save you more money in terms of reputational damage or lost customers and work time.

How it works

Server redundancy works using two servers that house identical data and functions. One is the primary, which is live online and working. The other is the redundant server, which is not live.

With the hardware ready, a ‘heartbeat’ system connects the primary server with the redundant one. If there’s a signal from the primary server, the redundant one remains inactive. If that signal changes, the redundant server can take over automatically.

Another option is a manual switch. An automated alert can inform a team member when something goes wrong with a primary server. From there, that team member can authorise a swap to the redundant server to get things running smoothly again.  

What is server redundancy?

Server redundancy, in its simplest terms, means having a backup server ready and waiting in case yours fails.

The goal of redundancy is reliability. It’s a contingency — a plan for when life gives you lemons in the form of an IT disaster.

Useful links

What is a server? An overview in 500 words or less

ELI5: what is failover?

Using automation for cyber protection