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-What is the TIA-942 Standard?

TIA is the Telecommunications Industry Association. TIA is member driven and delivers value to those involved in telecom, broadband, mobile wireless, information technology, networks, cable, satellite, unified communications, emergency communications, and the greening of technology.

The 942 standard was originally published in 2005 to describe the telecommunications infrastructure standard in data centres. Today the standard covers a large array of information related to guidelines for the design, build, and operations of data centres or computer rooms. Still related to it's original roots, the document has guidelines for: data centre design, cabling system infrastructure, telecommunications spaces/topologies, cabling systems, cabling pathways, redundancy, and informative annexes.

If you are interested in more, see the FAQ on data centre tiers.

-What is the difference between Tiers “1 2 3 4” and “I II III IV”?

Tiers are a point of significant confusion in the data centre industry. The origin of Tiers came from the Uptime Institute [founded in 1993 as Site Uptime Network] to help define "uptime" [not redundancy].

The Uptime Institute classified data centres into Tiers in Roman numerals I through IV where Tier IV represents the highest level of projected availability. Their Tiers defined the meter stick for measuring data centre availability. Their original "Tier Standard" summarized the tiers into measured percentage of availability as follows:

  • Tier I: 99.671%
  • Tier II: 99.749%
  • Tier III: 99.982%
  • Tier IV: 99.995%

Many years have passed since the first Tier Standard document was written by the Uptime Institute and the more recent release of the document describes the Tiers much better than before.

In 2005, the TIA approved the Telecommunication Infrastructure Standard for Data Centres or TIA-942 Standard. This standard also defines data centres into Tiers. They use Hindu-Arabic numerals, again Tier 1 through 4 where Tier 4 that are based on the Uptime Institute's Tiers.

The TIA-942 standard is written as guidelines or common/best practices. TIA Tiers are better understood as general levels of redundancy [as opposed to availability with the Uptime Institute].

  • Tier 1: N or "just enough"
  • Tier 2: N+1 [but not for all systems as generator is still N]
  • Tier 3: 2N [dual utility feeds (active and dormant) and N+1 power components]
  • Tier 4: 2(N+1) [dual active utility feeds]

For more information on Uptime Institute's Tiers and TIA-942 Tiers, please visit their respective websites.

-What Tier of data centre should I aim for?

Well, in short, the answers is "the one that suits your business requirements".

A Tier IV or even a Tier 4 data centre doesn't guarantee uptime or quality of service. But when managed properly, they do have the ability to deliver better availability than a lower Tier. In some cases when comparing availability, a Tier I facility has outperformed a Tier III facility.

Whether you are investigating a co-location facility or concerned about your own facility, look at the operational procedures and maintenance practices. In our opinion, these are more important than the way a facility is designed and built.

Your IT architecture may allow you to operate two lower Tier facilities in two different regions. When managing budgets, the operating costs of a higher Tier facility are much greater than lower Tiers.

-Can Impendo Tier certify my data centre?

This is a very common question.

  • For Uptime Institute: No, but we can help you achieve certification.
  • For TIA-942: Only compliance audit exists. Yes we can perform compliance audits.

If you need to achieve Uptime Institute facility certification, the only body that can certify your facility is the Uptime Institute themselves. They have a register of all certified facilities [along with certified design documents] on their website available to the public.

Uptime Institute Accredited Tier Specialist or Designer [ATS or ATD] do not have the right to certify facilities or certify for operational sustainability.

-How do I convert kW to Tons of cooling?

We use a conversion factor of 3.5168 kW/Ton of cooling. The theory is below.

  1. Fact: 1 kWh = 3412.142 BTU
  2. Fact: 1 Ton of cooling capacity = 12,000 BTU/h

Therefore, 1 Ton of cooling = (12,000 BTU/h)*(1 kWh)/(3412.142 BTU) = 3.5168 kW.

So if you want to figure out how many Tons of cooling is required for x number of kW of power consumed [or heat generated], simply divide the total kW by 3.5168. Keep in mind these are theoretical [perfect conditions] used for approximate designs; apply some sensible margins for error.