What is the Data Center Tier System?

Rating Data Centers:
Uptime Institute’s Data Center Tier Classification System

What is the Tier System?
The Tier Classification System refers to a benchmarking system from Uptime Institute to determine the availability, or uptime, of a data center. A number of factors determine what tier a data center falls under, including: power, cooling and ancillary data center systems. Each higher Tier delivers more uptime, data center performance, and requires more investment. Data centers range from Tier I to Tier IV, with each tier incorporating the lower tier’s requirements. Each tier is progressive, with Tier I being the simplest and Tier IV being the most resilient. Tier III is a common commercial solution for colocation and wholesale data center service providers. Tier IV data centers are designed for risk averse businesses with mission critical applications. Data centers use the following criteria to determine which Tier a facility falls under:


Example of Tier III Facility Certified by Uptime Institute

Tier I Basic Capacity data centers have a single path of power using an uninterruptable power supply (UPS) to handle short outages, dedicated cooling systems, and engine generators for extended outages. A Tier I data center must have its own dedicated space, as well as, a dedicated site infrastructure for IT support outside of the office. Tier I data centers offer no redundancy.
Tier II Redundant Component data centers, like Tier I data centers, they have a single path for power and cooling distribution and add redundancy, using equipment such as UPS modules, chillers or pumps, and engine generators which protect it from interruptions in IT processes.
Tier III Concurrently Maintainable data centers have redundant components and multiple distribution paths to allow for no shut downs for maintenance, repair or replacement of equipment. Tier III data centers have active power and cooling distribution paths with dual corded IT equipment.
Tier IV Fault Tolerant data centers offer multiple power and cooling distribution paths with autonomous response to failure. Tier IV data centers are self-healing in the case of faults, are compartmentalized to limit impacts of a single major fault and have Continuous Cooling for the transition from utility power to engine generators. Like Tier III data centers, IT equipment is dual corded, so that in the event of equipment failure, IT operations would not be interrupted.

We asked industry experts, Keith Klesner, SVP, North America at Uptime Institute, and Jose Ruiz, VP of Operations at Compass Data Centers about Uptime Institute’s Tier classification system and certification.

How Do I Choose Which Tier Fits My Business Model?
One tier is not better than another. How a company chooses what tier their facility should be is dependent on the needs of its data center. For example, a small law firm may have a Tier I facility, while a large scale e-commerce website may require a Tier III or Tier IV facility. “It really depends on what the company’s needs,” says Jose Ruiz. “Because the tiers are based on the uptime of the facility, the company needs to ask itself if it is okay with going down from time to time,” Ruiz continued. “For example,” he says, “A cloud application provider that is already replicating its data elsewhere may not need a Tier III or IV facility, and a Tier II system will suffice.” Ruiz stated, “On the other hand, a large financial institute, where the uptime is much more mission critical, would more than likely require a Tier III or Tier IV facility.”
The operations plan on how the facility will be managed also plays a huge role. “What Tier facility you plan to use largely depends on the criticality of the business and how you plan to operate long term,” said Klesner. “What operations model are you using and how do you plan to staff your facility? Well-staffed, minimal staff, or even a lights out data center? This will impact the topology choice in your data center design and construction.” Uptime Institute also offers certifications for a facility’s operations. Ruiz suggests, “If you follow what Uptime suggests for operations, then you will have a very well run data center.”

What are the Costs of Not Having a Properly “Tiered” Facility?
The costs of having a data center that meet Uptime’s requirements for a tiered facility vary based on the facility’s business model. The real question a business should be asking itself is, what are the costs of not meeting these specifications? “A company should always take into consideration the cost of an outage,” Keith Klesner told us. “And not just the direct costs, but also the indirect costs.” Klesner used Jet Blue’s recent mishap as an example. “Hundreds of flights were delayed due to their outage, and may result in future business loss.”
Not having a properly tiered facility can be costly due to prolonged periods without proper maintenance. “Non-tiered facilities may have their maintenance deferred which can eventually cause catastrophic outages.” Klesner stated. “These outages can cause vulnerabilities in infrastructure which can be very costly to the business.”

Not All “Tiered” Facilities are Actually Certified
While data centers may advertise themselves as a certain tier based on their design, the tier classification system refers exclusively to the certifications from Uptime Institute. A large number of facilities claim that they are Tier III or Tier IV facilities, but in reality, many fewer of those are actually certified as being so. A large number of companies have been marketing themselves as tiered facilities, or have engineered it to a certain standard, without actually having any sort of certification, and using ‘tier’ as a shorthand for the level of redundancy of their system. Klesner stated, “A self-certified data center is just that. As the IT industry transitions to data center service providers the industry is demanding certification from independent experts like the Uptime Institute.”

Why a Company Should Get Certified?
Many companies feel like they do not need to have their facilities certified or that it’s too costly of an endeavor. If a company can just engineer itself to a certain tier, what purpose or good would a certification do? Ruiz strongly suggests that facilities get certified to give a company peace of mind with unbiased 3rd party reassurance. “If a company requires a ‘tiered’ facility, they should also require a certification for that peace of mind,” he says. “People should carefully read the standards and reach out to Uptime Institute.” “People may think it is too expensive to justify the costs, but without the certification you lack the 3rd party validation.” He went on to explain, “Uptime Institute offers free resources about the certification process and standards.”
Ruiz also suggested that data centers should get both, the on-paper design of the facility certified, as well as the constructed facility. “Some providers might certify a design but find a way to reduce costs during the actual construction.” He used an instance at Compass as an example on why it is important to have both certifications. “We already had our design for the data center certified by Uptime and were having the actual construction of the facility certified. As we were performing a demonstration, some breakers went down. It turns out the breakers were incorrectly wired and labeled and as a result the demonstration failed. You don’t have those issues vetted out on the paper design. Correcting the label positions fixed the problem, but it was an instance where if we did not certify the constructed facility it could have resulted in a major outage.”

What Does the Industry Have to Say About the Standard?
Overall, the industry is very positive about Uptime Institute’s classification system. “The Tier system is a fantastic standard for our industry to classify Data Centers,” said Ruiz. “Data centers don’t all have the same needs.” Ruiz praised Uptime Institute’s classification system by saying, “Uptime Institute’s certification system is probably the only system out there that does a good job due to the amount of attention they put into it.” Ruiz said that the classification system has played a crucial role at Compass Datacenters. “The certifications they offer reassure us that our data centers are what we intended them to be and what we market to our customers.”

Further Reading
Tier Classification System
Explaining Uptime Institute’s Tier Classification System
Digital Realty, Uptime Debate Tier System

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