Data Center Tiers and What They Mean


If a Host says they run their operation in a Tier 2 data center, what does that mean? Along time ago, it was decreed to categorize data centers by tiers. Currently there are four tiers to the system (this system is not to be confused with Internet Backbone tiers, which are a different system entirely), aptly named Tier 1, Tier 2, Tier 3, and Tier 4.

Tier 1
Tier 1 was put into effect in 1965. Tier 1 is the data center with the least amount of redundancy and availability. It is the most basic data center. With a Tier 1, you are looking at:

  • Delivery Paths (between server and Internet): 1
  • Site availability: 99.671%
  • Redundant Components: None
  • Annual IT downtime: 28.8 hours

Tier 2
Tier 2 was mandated in 1970. With the increase of technology came an increased need for better data centers. Tier 2 is a slight upgrade to the Tier 2. With a Tier 2, you are looking at:

  • Delivery Paths (between server and Internet): 1
  • Site availability: 99.749%
  • Redundant Components: Redundant server hardware
  • Annual IT downtime: 22 hours

Tier 3
Tier 3 was mandated in 1985. Tier 3 marked a new change in data centers. Tier 3 was when multiple power and cooling paths was added and a large stride in reducing downtime occurred. With a Tier 3, you are looking at:

  • Delivery Paths (between server and Internet): 1
  • Site availability: 99.982%
  • Redundant Components: Power, cooling, and hardware redundancy
  • Annual IT downtime: 1.6 hours

An example of a Tier 3 data center is Tata Communication’s London Data Center.

Tier 4
Tier 4 came out in 1995. Tier 4 was another change in data centers. It is often remarked that ISPs upgraded all of their cable accept for that last mile. In data centers, the difference between Tier 3 and Tier 4 is that last mile. Tier 4 data centers added redundancy to the delivery paths enabling higher availability. Tier 4 is currently the pinnacle of data centers. With a Tier 4 you are looking at:

  • Delivery Paths (between server and Internet): 2
  • Site availability: 99.995%
  • Redundant Components: Redundant power, cooling, hardware, fault tolerance
  • Annual IT downtime: 0.4 hours

An example of a Tier 4 data center is SuperbInternet.net’s data centers.

So that’s the skinny on the tiers of data centers. I hope this ends any confusion on how the levels of data centers affect you. Until next time, happy hosting!

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Categories : Commentary


  1. […] Data centers are rated from Tier 1 (the closet in your office) to Tier 4 (can stay online during a major disaster and last 3 days without power). Tier 3 centers provide extremely high levels of security, power, speed, redundancy and disaster preparedness. Read about data center tiers and what they mean. […]

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