A comprehensive, reliable IT infrastructure can’t be overlooked!
While no business has the means to fully account for possible downtime, running a high availability (HA) system can reduce risks and keep IT systems functional during disruptions.
To achieve high availability, critical servers are grouped into clusters, where they can quickly shift to a backup server if the primary one fails. IT teams typically aim for at least 99.9% uptime and use strategies like redundancy, failover, and load balancing software to distribute the workload and minimize downtime.
High availability, or HA, is a process that removes single points of failure within an IT system. The goal is to maintain continual operations during both planned and unplanned system outages or downtime, guaranteeing reliability for internal and external users.
Achieving high availability involves using various strategies and tools. The approach below helps maintain system operations smoothly, even during failures or disruptions.
Businesses must account for the following components when setting up high availability systems.
High availability clusters involve groups of connected machines functioning as a unified system. If one machine in the cluster fails, the cluster management software shifts its workloads to another machine. Shared storage across all nodes (computers) in the cluster ensures no data is lost, even if one node goes offline.
Whether it’s hardware, software, applications, or data servers, all pieces of the system must have a backup so that when a component of the wider system fails, another is there to jump in and take over those operations.
When a system becomes overloaded, outages become more likely. Load balancing helps distribute the workload across multiple servers to avoid putting too much onto one particular area of the system.
The failure of a primary system is usually what requires another part of a high availability system to take over. Being able to automate this process by transferring operations to a backup system instantly is known as failover. These servers should be located off-site to provide greater protections if the outage is caused by something at your facility or primary location.
All elements of a high availability cluster need to be able to communicate and share information with each other during downtime. This is why replicating data across different geographical locations and data centers is vital for data loss prevention – if one area goes down, the others can handle the workload until maintenance provides a fix.
No system will ever achieve 100% availability, but IT teams that use HA systems want to get as close to it as possible. The most common measure of high-availability systems is known as "five nines" availability.
This term refers to a system being operational 99.999% of the time. Such high availability is typically required in critical industries like healthcare, transportation, finance, and government, where systems have a direct impact on people’s lives and essential services.
In less critical sectors, systems usually do not require this level of uptime and can function effectively with "three or four nines" availability, meaning 99.9% or 99.99% uptime.
Some other uptime-focused metrics that measure the availability of systems include:
MDT is the average time that a part of the system is down, both on the front and back end of the system. Keeping this number as low as possible minimizes customer service issues, negative publicity, and lost revenue. For instance, if the average downtime falls below 30 seconds, the impact is likely small. But 30 minutes or even 30 hours of downtime will damage operations.
MTBF is the average time a system is operational between two failure points. It’s a good indicator of how reliable the software or hardware is and helps businesses plan for possible future outages. Tools with larger MTBFs may need more frequent maintenance or planned outages to prevent failures that cause extensive unplanned downtime.
RTO refers to the amount of time the business can tolerate downtime before the system needs to be restored, or how long the company takes to recover from disruptive downtime. Businesses must understand the RTO of all parts of the system.
RPO is the maximum amount of data that a business can lose during an outage without sustaining a significant loss. Companies need to know their RPO in order to prioritize outages and fixes based on operational necessity.
Learn the difference between RTO and RPO.
Availability = (minutes in month - minutes of downtime) * 100/minutes in month
High availability focuses on software rather than hardware. Fault tolerance is largely used for failing physical equipment, but doesn’t account for software failures within the system. HA processes also use clusters to achieve redundancy across the IT infrastructure, which means that only one backup system is needed if the primary server fails.
Fault tolerance refers to a system’s ability to function without interruption during the failure of one or more of its parts. Similar to high availability, multiple systems work together so that the other parts can keep operations running.
However, fault tolerance requires complete hardware redundancy. In other words, when a critical or main piece of hardware fails, another part of the hardware system must be able to take over with no downtime. Fault tolerance calls for specialized tools to detect failure and enable multiple systems to run simultaneously.
Disaster recovery (DR) is the process of restoring systems after significant disruptions, such as damage to infrastructure or data centers. The goal of DR is to help organizations recover quickly and minimize downtime. In contrast, high availability prevents disruptions caused by smaller, localized failures, so systems operate smoothly.
Additionally, while DR and HA address different challenges, they share some similarities. Both aim to reduce IT downtime and utilize backup systems, redundancy, and data backups to manage IT issues effectively.
No matter the size of the business, unplanned outages can result in lost data, reduced productivity, negative brand associations, and lost revenue. Businesses should establish high availability as soon as possible to benefit from its advantages.
Updates to the IT system often require planned downtime and reboots. This can cause as many issues to users as unplanned outages, but planning ahead within a high availability system means that interruptions are infrequent. During planned maintenance, IT can back up these tools on a production server so that users experience little to no disruptions.
Continually-operating systems protect data from possible cyber threats and the loss of data that they can cause. Unauthorized users and cybercriminals will often target IT downtimes, particularly unplanned outages, to steal data or gain access to parts of the IT system. They can also cause this unplanned downtime through hacking attempts that can be even more difficult for businesses to recover from if a high availability process isn’t in place.
Even rare outages can frustrate your customers and ultimately leave them feeling uneasy trusting your business. Customer churn rates can increase as a result of outages, so you have to keep your systems operational to increase customer retention. If you do have an unplanned outage and there is some element of unavailability in the system, communicate with customers about it frequently.
While an HA system comes with many tangible benefits, there are also challenges that businesses need to be aware of before moving forward with this type of IT strategy.
A critical part of creating a high-availability IT system is making a plan for load balancing if your business experiences unexpectedly high levels of traffic to a server, network, or application. These load balancing tools redistribute traffic across the rest of the infrastructure to reduce traffic flow to a single system and minimize potential damage and downtime.
Above are the top five leading load balancing software solutions from G2’s Winter 2025 Grid Report.
Whether you’re trying to balance the uptime of multiple applications or looking for effective backups for your servers, implementing a high availability system will minimize disruptions at your business. So what are you waiting for? Get upgraded!
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