The tier-rating system for data centres is defined by the Uptime Institute. The rating system classifies how the infrastructure of a data centre is designed, managed and operated. It aims to give unbiased guidance to a business looking for a data centre to house its operations.
Tier I – Basic Capacity
Infrastructure in a tier I data centre provides a dedicated space for IT systems, an Uninterruptible Power Supply (UPS) to protect against spikes and sags in power and brief outages; dedicated cooling equipment that is never switched off and will run 24/7; and a backup generator to power IT equipment during extended power outages.
Tier II – Redundant Capacity Components
A tier II data centre will have redundant power and cooling equipment such as UPS modules, chillers, pumps and backup generators. This will enable some maintenance to be carried out with lower disruption to the data centres operations and also increase the safety margin against interruptions caused by equipment failures.
Tier III – Concurrently Maintainable
Without shutting down anything a tier III data centre can maintain and replace equipment. An additional, redundant supply of both power and cooling is added to that already provided by tier II so that every component can be shut down and maintained with no disruption to the IT operations.
Tier IV – Fault Tolerance
Building on the infrastructure of tier III, fault tolerance is added to the site. This means the IT operations of the data centre will not be affected by individual equipment failure or distribution interruptions.