Data Center Tier Levels

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Data Center Tier Levels are a standard methodology used to determine a data center’s ability to maintain functionality during different types of failures, such as power outages. The higher the tier level, the more sustainability for data center operations and fault-tolerance systems that will allow for efficient use during certain kind of emergencies.

Developed by the Uptime Institute - a global research organization - the tiered system offers organizations a way to evaluate return on investment (ROI) and performance. It is comprised of a 4-tiered scale, with Tier-IV being the most robust.

Uptime Institute is responsible for providing certificates to data center facilities.

The 4 tiers as categorized by the Uptime Institute are:

Tier-I: It’s composed of a single, non-redundant path for distribution, power and cooling with providing 99.671% uptime.

Tier-II: Composed of a single, redundant path for distribution, power and cooling with providing 99.741% uptime.

Tier-III: It has typically more comprehensive protection for power outages and have what’s called N+1 redundancy, a reliable backup power system.

Tier-IV: It tops the level. It represents a data center facility that has the infrastructure, capacity, and processes in place for providing maximum level of uptime. Apart from all requirements for Tiers I, II and III, Tier-IV requires the infrastructure that is fully fault-tolerant. It should function normal even in the event of failure of one or more equipment. It will have multiple cooling units, backup generators, power sources, chillers etc. In the event of failure of one of the equipment, another will start up replacing its output instantly.


1. Colocation server