Ben Hatton Data Center Tiers Explained

February 21, 2014 by · Leave a Comment 

One word that you often see associated with any data center is its “tier,” or its level of service. Virtually every data center has a tier ranking of I, II, III, or IV, and this ranking serves as a symbol for everything it has to offer: its physical infrastructure, its cooling, power infrastructure, redundancy levels, and promised uptime. Data Center Tiers

We consider Data Cave to be categorized as a Tier IV data center because of our best practices and maximum uptime levels.  But apart from looking good on paper, what does that actually mean to you? I wanted to use this post to answer that question! I will cover what each of the 4 data center tiers encompass, what types of factors go into each tier ranking, and what it ultimately means at the end of the day.

Some Background

The data center tier system first came into existence back in 2005, as a way to bring quantifiable standards to the industry that can be measured against for each individual data center. These standards were developed and are maintained by the Telecommunications Industry Association (TIA), an entity that is responsible for a wide range of standards across many spectrums of the IT industry. In addition, a separate set of 4 tier levels has also been developed by the Uptime Institute, a 3rd party data center research organization. While these different sets of standards are maintained separately by these two organizations, they are very similar to one another in terms of the specific criteria that make up each tier.

The Tiers

Each data center tier ranking consists of several criteria and requirements that primarily focus on a data center’s infrastructure, levels of redundancy, and promised level of uptime. Here are some specifics on the factors that go in to each of the 4 tiers:


Tier I A Tier I data center is the simplest of the 4 tiers, offering little (if any) levels of redundancy, and not really aiming to promise a maximum level of uptime:

  • Single path for power and cooling to the server equipment, with no redundant components.
  • Typically lacks features seen in larger data centers, such as a backup cooling system or generator.
  • Expected uptime levels of 99.671% (1,729 minutes of annual downtime)
Tier II The next level up, a Tier II data center has more measures and infrastructure in place that ensure it is not as susceptible to unplanned downtime as a Tier 1 data center:

  • Will typically have a single path for both power and cooling, but will utilize some redundant components.
  • These data centers will have some backup elements, such as a backup cooling system and/or a generator.
  • Expected uptime levels of 99.741% (1,361 minutes of annual downtime)
Tier III In addition to meeting the requirements for both Tier I and Tier II, a Tier III data center is required to have a more sophisticated infrastructure that allows for greater redundancy and higher uptime:

  • Multiple power and cooling distribution paths to the server equipment. The equipment is served by one distribution path, but in the event that path fails, another takes over as a failover.
  • Multiple power sources for all IT equipment.
  • Specific procedures in place that allow for maintenance/updates to be done in the data center, without causing downtime.
  • Expected uptime levels of 99.982% (95 minutes of annual downtime)
Tier IV At the top level, a Tier IV ranking represents a data center that has the infrastructure, capacity, and processes in place to provide a truly maximum level of uptime:

  • Fully meets all requirements for Tiers I, II, and III.
  • Infrastructure that is fully fault tolerant, meaning it can function as normal, even in the event of one or more equipment failures.
  • Redundancy in everything: Multiple cooling units, backup generators, power sources, chillers, etc. If one piece of equipment fails, another can start up and replace its output instantaneously.
  • Expected uptime levels of 99.995% (26 minutes of annual downtime)


What Tier IV Represents

As you can imagine, there are A LOT of factors that go into the data center tiering system, and following many of the established best practices for a specific tier are very well worth it. Being categorized under a data center tier provides the clearest, most recognizable symbol of that data center’s capabilities. Data Cave is categorized as a Tier IV data center, because we consistently follow all of its established guidelines, as well as maintain maximum uptime levels. It is a simple and clear indicator that fully describes our facility, infrastructure, processes, and how we compare to other data centers.

Now that you know a bit more about the 4 data center Tiers, and what goes into each ranking, would you like to see firsthand what a Tier IV data center looks like?  If so, Contact us today to schedule a facility tour!

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