To differentiate the capabilities of data centres, industry authority Uptime Institute has developed a four-tier classification system.

The system seeks to categorise, and evaluate data centre facilities in terms of site infrastructure, and uptime performance.

The tiers are progressive in nature, and each tier incorporates the capabilities of all tiers below it.

Infrastructure, maintenance, and compliance costs increase with every tier levels.

Tier I: Basic Capacity

Tier I data centres provides dedicated site infrastructure to support information technology services beyond basic office settings.

Facilities that a Tier I data centre feature include at least one uninterruptible power supply (UPS) system, a dedicated cooling equipment that runs beyond office hours, and a designated power generator that protects IT functions from extended power outages.

Tier II: Redundant Capacity Components

Tier II data centres are equipped with redundant UPS, generators, and cooling equipment that provides an increased margin of safety against infrastructure failure.

Given this additional redundancy, select maintenance tasks can be carried out on the property, without the need to take it offline.

Tier III: Concurrently Maintainable

Tier III data centre properties do not require shutdowns when critical equipments need to be replaced, or maintained.

The properties are equipped with redundant UPS, generators, and cooling equipment, but also feature alternate delivery channels for these power and cooling systems.

Tier IV: Fault Tolerance

Tier IV data centres builds on features found in Tier III, but incorporating fault tolerance features in its site infrastructure topology.

Fault tolerance is a concept that ensures the continuity of IT operations, despite individual equipment failures, or interruption in distribution paths.

This is currently the highest tier in the data centre properties classification system, and is usually sought after by multinational corporations offering critical IT systems.

This entry is part of REITsWeek's glossary of REITs and real estate investment terms.

By Ridzwan Rahmat

Ridzwan has been analysing REITs and business trusts since 2008, and personally manages a portfolio comprising mainly of SGX-listed REITs. He founded REITsWeek in 2013.