Established by the Uptime Institute (TUI) in the 1990s, the data centre Tier classification system is used to organise specific types of data centre infrastructure in a consistent way. Based on a set of operating criteria, the system comprises 4 progressive classifications starting at Tier 1 and ramping up to Tier 4. The Tiers typically take Roman Numeral form on the certification.
The Uptime Institute have left some ambiguity around how the Tiers are defined, however, they have made the most important metrics common knowledge. These metrics include, power availability, uptime guarantee, cooling capacity and concurrent maintainability, to name a few.

The classifications help data centres and customers alike to identify the level of redundancy and complexity that a data centre infrastructure provides and assists in ensuring that the correct size UPS is installed.

Looking further into the power aspects of the tiering system, having a redundant electrical path for power is crucial for achieving the higher Tier status. A data centre must satisfy the requirements of the previous Tier before moving upward to the next one

What is a Tier 4 (Tire IV) Data Centre?
To achieve Tier 4 certification, a data centre must meet all criteria set out in Tier 3 + Tier 2 + Tier 1 + additional criteria to provide customers with the highest levels of availability and 99.995% uptime per annum.

There must be zero single points of failure in a Tier 4 data centre with redundancies for every process, including the UPS (uninterruptible power supply). This is achieved by implementing a critical infrastructure with a minimum redundancy configuration of N+N (distributed redundant) or better still 2N+1, whereby there is two times the amount of power required, plus a backup supply.

Each UPS can carry the entire critical load and supports its own independent distribution system with no power connections between each one. Multiple power distribution units (PDUs) are used for distributing the electrical power between the critical load and independent UPS units. All downstream loads can be switched to one of the UPS units allowing the others to be taken offline for maintenance or load reconfiguration.

This is the most expensive option for customers to buy into and is also the most expensive data centre to design. For this reason, it is typically used by large, global businesses or public sector organisations. Customers requiring this level of facility will have the budget to sustain residence and will typically be hosting mission-critical servers.

What is a Tier 3 (Tier III) Data Centre?
With a minimum uptime requirement of 99.982% and no more than 1.6 hours of downtime per annum, a tier 3 data centre is the facility of choice for most small/medium sized businesses. It comprises all the credentials of a Tier 2 + Tier 1 + the requirement of having dual powered equipment and multiple uplinks. The critical infrastructure should be configured in a N+1 arrangement meaning it can undergo routine maintenance without affecting operations.

What is a Tier 2 (Tier II) Data Centre?
To be defined as Tier 2, a data centre must have redundancy on the most critical aspects of its mechanical structure; power and cooling distribution. This means that during planned maintenance outages, the level of uptime won’t be affected. To be certified to this level, a data centre must achieve 99.741% uptime per annum.

Tier 2 data centres are typically targeted to SMEs. They offer significantly higher levels of efficiency than Tier 1 without the expense of a Tier 3 site.

What is a Tier 1 (Tier I) Data Centre?
Considered the least reliable of data centre architecture, a Tier 1 data centre does not include any redundant on any part of its operations. These facilities allow the highest amounts of downtime, requiring only 99.671% of uptime per annum.

If a Tier 1 data centre experiences a power outage, it is likely that customers of the facility will incur downtime due to the lack of backup systems in place. Customers will also find themselves out of action at every maintenance interval as data centres under this certification are not required to have an additional power supply while the facility undergoes maintenance.

Choosing the Right Data Centre Tier
As the Uptime Institute are somewhat discrete about their ranking criteria, earning an official rank is difficult and there are no guarantees that investing in additional infrastructure will warrant a specific classification. The higher up the levels a data centre climbs, the more difficult it is to achieve the next level.

Having a UPS supplier that is knowledgeable in the classifications will make the process of designing or upgrading the data centre to the desired Tier rating smoother. It is also important to remember that It’s not just a case of installing the critical infrastructure, to ensure consistent reliability from the UPS, a maintenance schedule from a reputable UPS maintenance provider is essential.

Our modular UPS manufacturing partner, Huawei, show their continued commitment to the data centre industry by being apart of the TIER-Ready programme. Power Control is a long standing partner of Huawei, supplying, installing and maintaining their centralised modular UPS solutions. Available up to 21MW, their UPS systems are ideal for higher Tier data centres to ensure reliable redundancy.

Power Control has also partnered with modular UPS manufacturer Legrand, and stand alone UPS manufacturer, Borri SPA. To find out which topology is most suitable for your data centre’s needs, contact us 01246 431431 or email info@powercontrol.co.uk.