In the digital age, businesses increasingly rely on third-party data centres to provide highly available environments that support critical workloads. However, usability can mean something different for each organization as their needs, expectations and budgets differ. When it comes to web hosting, your choice between data centre types is as important as your server selection. Since 1987, Uptime Institute acts as an impartial advocate for the enterprise data centre industry. It would be wrong to think that all data centres should be the same. To choose the right data centre solution, the concept of layers must first be understood. Tier classification levels remain the international standard for data centre performance today. Understanding data centre tiers and types helps IT teams differentiate between the productivity, uptime, structure, and design that each tier and type offers. A data centre tier classification system can be valuable to companies in how their business goals align with the reliability of their data centres.

Data centre tiers, created by the Uptime Institute, are rankings created for the performance of servers hosting data and information. Data centre tiers define the infrastructure required for data centre operations. There are different layers according to the system needed. The classification system defines a benchmark for the data centre industry. These degrees are objective and reliable methods used to align infrastructure structure, performance, and investments with business objectives. Data centres are ranked from I to IV. Each of the four data centre tiers reflects a specific and increasing level of performance, redundancy, and complexity. Tier IV does not mean data centre is better than Tier II. This means that the levels fit different business operations. The higher the tier level, the higher the costs. The tiers are flexible enough to allow many solutions that meet performance targets and compliance regulations.

Each tier is tightly defined based on several factors, including uptime guarantee, staff expertise, maintenance protocols, and more. Below you can find the data centre tiers specified by the Uptime Institute. These are:

Tier I data centre is the most basic type of data centre facility. It is the basic capacity level with infrastructure supporting information technology for an office environment and beyond. Small businesses with limited budgets are the most suitable users for these centres. Tier I infrastructure includes:

• • An area dedicated to IT systems
• • Cooling equipment operating after hours
• • An uninterruptible power supply (UPS) to filter power spikes, dips, and momentary outages
• • A motor generator

A Tier I data centre with limited flexibility guarantees a minimum of 99.671% uptime per year, resulting in a maximum of 28.8 hours of downtime per year. Downtime is tolerable for small businesses and start-ups that don't have complex requirements or round-the-clock operations.

Tier II facilities include all Tier I capabilities and offer additional options. These additional options increase reliability to 99.741% annual uptime or 22 hours of downtime. These facilities still use a single distribution path for power and cooling and are susceptible to unexpected outages. The Tier 2 data centre includes the following components: Engine generators, energy storage, chillers, UPS modules, pumps, heat rejection equipment, fuel tanks and fuel cells.

SMBs generally prefer to use at least one Tier III rated system for the far superior redundancy protections offered. Tier 3 offers 99.982% uptime for years and 1.6 hours of annual downtime. A redundant distribution path is added for power and cooling to the redundant critical components of Tier II. Thus, each required component can be shut down and maintained without any impact on the IT operation.

It is often used by businesses that require constant availability. They have a 99.995% uptime, meaning no more than 26 minutes of downtime per year. The purpose of a Tier 4 data centre is to provide ongoing support and service no matter what, and is the highest classification provided by the Uptime Institute. Tier IV data centres are ready for unscheduled maintenance. Businesses that often use Tier IV systems often don't even realize there's an outage.