A Guide to Data Centre Tiers

Data centre tiers are a crucial framework for aligning business requirements with a data centre provider. 

The tiering standard is a method used to describe and evaluate the reliability and service offering of a  data centre, in relation to business requirements.  

This article explains the differences between data centre tiers and how to use the tiering standard to choose the right data centre solution based on business needs. 

3 August 2022

What are Data Centre Tiers 

The data centre classification system focuses on performance, uptime guarantees and redundancy measures. It was first introduced by the Telecoms Industry Association, with an updated version released by the Uptime Institute.  

The tiers are generally consistent across the data centre industry, even if the designs of the data centres themselves are unique. They comprise of 4 performance levels that indicate the reliability of data centre infrastructure – Tier 1 through to Tier 4. The specifications for each tier are progressive, which means that a data centre which fulfils Tier 2 will fulfil all the requirements of Tier 1, plus those of Tier 2. 

For example: 

Tier 4 = Tier 3 + Tier 2 + Tier 1 


Data Centre Tier Ratings Overview 

Tier 1: Basic Capacity. A data centre that provides dedicated site infrastructure for IT systems. They are designed with a single input for power and for cooling, with little to no provisions for redundancies or outages. The expected uptime guarantee of this tier is 99.671% per year.  

Tier 2: Redundant Capacity. A data centre that also typically provides one path for power and cooling. However, Tier 2 data centres account for redundancies with extra equipment on site. The expected uptime guarantee of this tier is 99.941% per year. 

Tier 3: Concurrently Maintainable. A data centre designed with multiple paths for cooling and power, and measures for multiple redundancies. The expected uptime guarantee of this tier is 99.982% per year. 

Tier 4: Fault Tolerant. A data centre designed to have no single point of failure, with multiple power and cooling paths into equipment and more than one connection to the main power grid.The expected uptime guarantee of this tier is 99.995% per year. 


Data Centre Tiers Explained 

Tier 1 Data Centre 

Tier 1 data centres have been derisively referred to as ‘warehouses with power’, as the investment in these are usually driven by cost and time to market. They tend to be tactical choices for businesses that need support that fits in their budget or for businesses that don’t rely on real-time service outputs. 


Tier 2 Data Centre 

A Tier 2 data centre is very similar to a Tier 1 centre, as they typically have one path for power and cooling. However, this tier offers better protection against disruptions, with redundancy components such as extra cooling units, engine generators, and energy storage that can be used in the event of total outage. 


Tier 3 Data Centre 

Data centres classified as Tier 3 are the most common type used by businesses all over the world. Tier 3 data centre requirements include all of the prior tiers but add a layer of reliability and long-term viability for businesses looking for year-on-year support. Businesses use Tier 3 centres as strategic assets, as the infrastructures they form part of are built beyond their current IT requirements. With rigorous uptime requirements, they are designed with multiple paths for cooling and power. Measures for multiple redundancies are in place with additional equipment taking power and network connection from independent entries, allowing for concurrent availability. 


Tier 4 Data Centre 

Tier 4 is the highest possible classification for a data centre, and typically costs twice as much to build as a Tier 3 centre. This is because every piece of equipment in the facility has a backup powered independently, with a seamless transition in case of a failure. This calibre of data centre is built to have no single point of failure, with multiple power and cooling paths into equipment and more than one connection to the main power grid. This tier of data centre is not as common as the other tiers, but its fault-tolerant design makes it ideal for consistently high levels of traffic. 


How to Choose the Right Data Centre Tier 

When researching for enterprise IT solutions, it is imperative to ask the right questions, talk to the team running the facility to find out what kind of testing and monitoring they do routinely. Tier 3 fits the requirements for most businesses, with a balance between service and resource outlay. A strategic solution often splits requirements across multiple Tier 3 centres, giving your business a higher uptime than one poorly run Tier 4 data centre. 


Want to Explore More?  

Interxion has 14 London data centres and 6 interconnected colocation and scale data centre campuses, with the extension of the London Metro Connect, giving your business the ideal technology platform to grow.  

We act as your strategic partner, enabling access to diverse connected communities of interest, all within our data centres. 

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