High Availability vs Fault Tolerance


Whether you’re thinking about moving to a new data center, or you’re questioning whether or not to move away from your current in-house setup, you’ll likely already have a good idea of what you’re looking for. 

One of the key requirements that we often hear companies asking for is of course fault tolerance. If downtime is a concern for you, then this should certainly feature highly on your list of priorities. But did you know that high availability can provide a similar level of service? 

Why not take a moment to learn more about what terms like high availability and fault tolerance mean and how these options might affect the service you’re able to provide to your own customers? 

In this article, we’ll divulge all you need to know about fault tolerance and high availability, so you can make the best decision for your business. 

What is fault tolerance?

Fault tolerance is a hugely attractive offer in any data center. In short, it means that a data center will never come up against issues that would result in service interruption, and therefore, businesses will never be held back by problems relating to their chosen data center. 

For companies that rely on their online services to connect with customers and fulfill their obligations, fault tolerance is enormously important. But, of course, like all good things, it comes at a price. 

We have more information on what makes a data center fault tolerant, but to summarise, fault tolerant data centers are specially designed to ensure no single point of failure. 

Redundancy plays a big role in this, but this also means redundant components must be on standby at all times – and must be paid for whether they’re ever needed or not. This is why colocation data centers, like TRG’s, are so attractive. 

These facilities are built with fault tolerance in mind in order to mitigate the risks of downtime, but without users having to pay as much as they would for their own data centers. 

When fault tolerant hardware is used to its full advantage, the changeover to new components is entirely seamless. So, if you’re a company that prides itself on the fact that it never lets customers down, then this could well be the best option for you. But bear in mind that if you are able to tolerate a small amount of downtime, you could potentially be in the position to reduce your data center budget quite considerably. 

What does high availability mean? 

The term high availability also relates to the reduction of downtime through a carefully considered setup. High availability prioritizes the most important services to cut the risk of the most damaging interruptions, using shared resources to minimize downtime without escalating costs. 

If a system, component, or application runs into problems in a high availability setup, software, and hardware are both used to bring services back to life in what the system determines to be the quickest and most effective way. 

High availability doesn’t usually result in instant recovery like fault tolerance would, but downtime is commonly reduced to under a minute. Backup processors can also usually be used during these periods. 

For some companies, given that more essential services tend to be best protected, this is a good option. It’s often said to offer the best of both worlds: minimal service interruption along with more affordable pricing. 

Which is best: high availability or fault tolerance? 

We’re always asked whether fault tolerance is worth the investment or whether high availability is just as good (and much more affordable!) The answer to this of course varies depending on your needs.

The key thing to consider is what the cost of downtime would be for your company, and how this might vary depending on when the downtime occurred. 

If downtime was encountered during the busiest period for your company, what would this mean in terms of lost revenue? Think about this and weigh up how your business would cope with a limited amount of downtime over the year. 

Once you’ve narrowed down the answers to these questions, you’ll know exactly how much your company should invest in minimizing interruption. 

If your company could manage a limited amount of downtime over the year without incurring huge costs or eye-watering amounts of lost revenue, then you may well prefer to opt for a high availability system instead. 

In this case, look out for high availability data centers, and you’ll likely find a package that fits your company’s requirements. 

Run the numbers, and you may find that just a small amount of downtime would devastate your company. If this is the case, then we recommend that you investigate fault tolerance in more detail. 

Look into data centers that are built with fault tolerance in mind, as these will provide the most robust protection for your company. 

High availability vs fault tolerance: key differences

High availability and fault tolerance are critical aspects of system design, aiming to ensure that services remain accessible and functional despite failures. 

However, they approach this goal in different ways. Here are the primary distinctions:


  • High Availability (HA): The primary goal is to ensure that a system remains operational and accessible with minimal downtime. High availability systems are designed to recover quickly from a failure, ensuring that services are available as much as possible.
  • Fault Tolerance (FT): The focus is on enabling a system to continue operating without interruption, even when there are hardware or software failures. Fault tolerance involves designing systems that can operate normally in the event of a component failure.


  • HA: High availability accepts that some downtime can occur during a failure. The aim is to reduce this downtime to a very minimum, often aiming for the “five nines” (99.999% uptime) availability.
  • FT: Fault tolerance aims for zero downtime, ensuring that services continue without interruption even when individual components fail.


  • HA: Implemented through redundancy of components and quick failover mechanisms. When a component fails, the system quickly switches to a backup component or system without significant downtime.
  • FT: Achieved by having redundant components that can immediately take over the functions of a failed component without needing manual intervention or causing system downtime.


  • HA: Generally less expensive than fault tolerance because it allows for some downtime and does not require as many redundant components to be active and running simultaneously.
  • FT: More costly because it requires a more complex setup with multiple active components ready to take over instantly in case of failure, leading to higher hardware and maintenance costs.

Use Cases

  • HA: Suitable for applications where brief interruptions can be tolerated, such as web services, databases, and application servers that can afford short periods of downtime for maintenance or in case of failure.
  • FT: Essential for critical systems where downtime is unacceptable, including life support systems, financial trading systems, and other critical infrastructure that must operate without interruption.

In summary, high availability focuses on minimizing downtime and ensuring access to services as much as possible, accepting brief interruptions in service. 

In contrast, fault tolerance is about eliminating downtime altogether by designing systems that can continue to operate normally even when components fail. 

The choice between high availability and fault tolerance will depend on the specific requirements of the system being designed, including cost, complexity, and the critical nature of the services it provides.

Get in touch to find out more about fault tolerance

At TRG Datacenters, we believe that good infrastructure should be a default. Our Houston data center is designed with fault tolerance in mind, meaning our customers can rely on the service we provide, and their customers are never aware of any downtime or service interruptions at all. 

If you’d like to find out more about fault tolerance and what it could mean for your company, don’t hesitate to contact our team. We’re always on hand to talk new customers through what fault tolerance is and why it matters, and we’d be happy to explain it in more detail. Give us a call to speak to a member of our team.