Explaining the Uptime Institute’s Tier Classification System

Uptime Institute

Matt Stansberry has researched the convergence of technology, facility management and energy issues in the data center for over a decade. Since January 2011, he is Director of Content and Publications at Uptime Institute.

Uptime Institute’s Tier Classification System for data centers is approaching the two decade mark. Since its creation in the mid-1990s, the system has evolved from a shared industry terminology into the global standard for third-party validation of data center critical infrastructure.

Over the years, some industry pundits have expressed frustration with the Tier System for being confusing. In many cases these writers have misrepresented the purpose and purview of the program.

Invariably, these authors and interview subjects have never been involved with a Tier Certification project. Typically, the commentator’s understanding of the Tiers is entirely secondhand and ten years out of date. And yet, when a commentator manages “1 million square feet of data center space for a large multinational enterprise” and represents a respected organization like AFCOM, we feel the need to respond.

I would like to take this opportunity to explain what the Tiers look like today, illustrate how Tier Certification works, list some companies that have invested in Tier Certification and offer Uptime Institute’s vision for the future.

What are the Tiers?

Uptime Institute created the standard Tier Classification System to consistently evaluate various data center facilities in terms of potential site infrastructure performance, or uptime. The Tiers (I-IV) are progressive; each Tier incorporates the requirements of all the lower Tiers.

Summary definitions of the Tiers I-IV are available here.

Data center infrastructure costs and operational complexities increase with Tier Level, and it is up to the data center owner to determine the Tier Level that fits his or her business’s need. A Tier IV solution is not “better” than a Tier II solution. The data center infrastructure needs to match the business application, otherwise companies can overinvest or take on too much risk.

Uptime Institute recognizes that many data center designs are custom endeavors, with complex design elements and multiple technology choices. As such, the Tier Classification System does not prescribe specific technology or design criteria. It is up to the data center owner to meet a Tier Level in a method that fits his or her infrastructure goals.

Uptime Institute removed reference to “expected downtime per year” from the Tier Standard in 2009. The current Tier Standard does not assign availability predictions to Tier Levels. This change was due to a maturation of the industry, and understanding that operations behaviors can have a larger impact on site availability than the physical infrastructure.

Tier Certification

The Tier Certification process typically starts with a company deploying new data center capacity. The data center owner decides to achieve a specific Tier Level to match a business demand.

Data center owners turn to Uptime Institute for an unbiased, vendor neutral benchmarking system, to ensure that data center designers, contractors and service providers are delivering against their requirements and expectations.

The first step in a Tier Certification process is a Tier Certification of Design Documents (TCDD). Uptime Institute Consultants review 100% of the design documents, ensuring each subsystem among electrical, mechanical, monitoring, and automation meet the fundamental concepts and there are no weak links in the chain.

Uptime Institute has conducted over 400 TCDDs, reviewing the most sophisticated data center designs from around the world. As you might imagine, we’ve learned a few things from that process. One of the lessons is that some companies would achieve a TCDD, and walk away from following through on Facility Certification for any number of reasons. Some organizations were willfully misrepresenting the Tier Certification, using a design foil to market a site that was not physically tested to that standard.

The TCDD was never supposed to be a final stage in a certification process, but rather a checkpoint for companies to demonstrate that the first portion of the capital project met requirements. Uptime Institute found that stranded Design Certifications were detrimental to the integrity of the Tier Certification program. In response, Uptime Institute has implemented an expiration date on TCDDs. All Tier Certification of Design Documents awards issued after 1 January 2014 will expire two years after the award date.

Data center owners use the Tier Certification process to hold the project teams accountable, and to ensure that the site performs as it was designed. Which brings us to the next phase in a Tier Certification process: Tier Certification of Constructed Facility (TCCF).

During a TCCF, a team of Uptime Institute consultants conducts a site visit, identifying discrepancies between the design drawings and installed equipment. Our consultants observe tests and demonstrations to prove Tier compliance. Fundamentally, this is the value of the Tier Certification, finding these blind spots and weak points in the chain. When the data center owner addresses the deficiencies, Uptime Institute awards the TCCF letter, foil and plaque.

Does the industry find value in this process? The clearest proof is the list of companies investing in Tier Certification. There are more Certifications underway at this moment than at any other point in the 20-year history of the Tiers.

Look at adoption among the telecommunications companies, colocation providers and data center developers: Digital Realty, Compass Data Centers, CenturyLink, and Switch. We have been pleased to impress each and every one of those companies with our dedication to quality and thoroughness, because we understand all that is on the line for them and their clients.

As the IT industry moves further into the cloud and IaaS mode of IT service delivery, the end user has less control over the data center infrastructure than ever before. Tiers and Operational Sustainability provide third-party assurance that the underlying data center infrastructure is designed and operated to the customer’s performance requirements.

Here is the full list of Tier Certification awards.

Beyond Tiers: operations

As mentioned previously, Uptime Institute recognizes the huge role operations plays in keeping data center services available. To that end, Uptime Institute developed a data center facilities management guideline in 2010 (Tier Standard: Operational Sustainability) and certifies data center operations. This is a site-specific scorecard and benchmarking of a facilities management team’s processes, with an on-site visit and detailed report.

For companies with existing sites, or for whatever reason have not chosen to certify data center facilities against Tiers, the operations team can be certified under the Management & Operations (M&O) Stamp of Approval.

The key areas reviewed, observed, and validated include staffing, training and maintenance. The Full citeria are described in Tier Standard: Operational Sustainability.

By covering these essential areas, a management team can operate a site to its full uptime potential, obtain maximum leverage of the installed infrastructure/design and improve the efficacy of operations.

The path forward?

In addition to the certifications listed above, Uptime Institute is delivering and developing further services for the IT industry around corporate governance and IT resource efficiency. As we bring those services to market, we will commit to being more present in the public forum.

With further education in the market, we hope to engage in substantive debates about our processes and approach, rather than defending claims from individuals with incorrect or incomplete knowledge of the Tiers program.

Fundamentally, it is our responsibility to better explain our approach and intellectual property. We owe it to our hundreds of clients who have invested in Tiers Certification.

Industry Perspectives is a content channel at Data Center Knowledge highlighting thought leadership in the data center arena. See our guidelines and submission process for information on participating. View previously published Industry Perspectives in our Knowledge Library.


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  1. Matt, As the leading association for data center professionals, AFCOM serves the industry by providing vendor-neutral leadership and insight. While I understand your desire to reply to Hector’s opinion, I think you may have misunderstood what he was saying in his comments in the article you refer to. He states as we all know, the Tier level ratings are talked about by many, but understood by only those who have read and comprehend the information. As the President of AFCOM, I have heard some say they are a Tier 2.5, to which tells me they do not understand the Tier ratings at all. Hector was right as well stating “most who talk about Tiers aren’t certified by the Uptime Institute”. If everyone would take the time to dive into the information the Uptime Institute provides on the Tier ratings, there would not be confusion. But I think we both know that will most likely not happen. It is much easier to think you understand than to actually take the time to understand. Hector was not stating the ratings are confusing, he wanted to state many are confused on what they are due to lack of their knowledge, not due to the Uptime Institutes documentation on what they are. At AFCOM, we value and encourage healthy and productive debate on standards and guidelines within the industry. We believe such debate only makes the industry stronger. I personally would like to extend an invitation to you to present a session on Uptime Institute’s Tier Classification at the upcoming Data Center World Global conference. It would provide an excellent platform to provide further clarification and discussion among the world’s data center managers. Serving the data center industry. Tom Roberts AFCOM President

  2. Tom, I respect AFCOM and the work you have done there. The article stated that "Tiers are related to energy efficiency and not necessarily a reflection of reliability." Not the case. Also, the article called our company's core IP confusing. Mr. Diaz commented that Tier-rating is not the final arbiter of real-world availability, without mentioning that we addressed this issue specifically almost five years ago. I agree with you -- this was not a takedown piece on the Uptime Institute. But Data Center Knowledge is our industry's most respected, widely read publication and making dismissive statements about our IP and Services without any understanding of the current state of the standard or certifications was irresponsible. The article came to my attention because one of our large clients had asked if we were going to defend their investment in the Tiers. In some ways, the article is a mea culpa -- we need to be more active in the public discussion. And I look forward to having further discussions with you and your leadership team.

  3. mark Baldwin

    question? you require 12 inch separation between source A & B feeds. i am using overhead busway above the racks. Is this 12 inch . clearance between the A & B runs of busway,or the busway bar to the top of the data rack? Or from the bottom of the tap off box to the rack? tx, markb