Types and Tiers of Data Centers: A Primer Blog Feature
Blair Felter

By: Blair Felter on June 12th, 2018

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Types and Tiers of Data Centers: A Primer

data center tiers | Data Center

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Not all data centers are created equal. The Uptime Institute (UI), the IT industry’s most trusted global standard for the proper design, build, and operation of data centers, has developed strict standards in order to separate the very basic from the very best. Rather than assign grades, UI classifies data center types by four tiers. Each tier represents different levels of availability, hours of interruption per year, and data center facility and system redundancy standards.

Data center Tiers

Tier I Data Center

  • 99.671% minimum uptime
  • 28.8 hours of downtime annually
  • no redundancy

Tier II Data Center

  • 99.741% minimum uptime
  • 22 hours of downtime annually
  • Partial redundancy

Tier III Data Center

  • 99.982% minimum uptime
  • No more than 1.6 hours of downtime annually
  • N+1 redundancy (the facility has what is required to operate plus a backup)

Tier IV Data Center

  • 99.995% minimum uptime
  • .04 hours of downtime annually
  • 2N+1 redundancy (the facility has two times what is required to operate plus a backup)

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Advantages of Uptime and Costs of Downtime

Uptime refers, of course, to how quickly a data center can have an organization up and running following a disaster, whether it’s a power outage, a natural disaster, or a data breach. You’ll notice the minimum uptime is over 99% for every tier, with differences of less than one percent—so one may think it’s safe to assume uptime is similar across tiers. But these fractional slices of time do add up. A Tier I data center can be down 28.8 hours in the course of a year, while a Tier IV data center has an annual maximum downtime of 0.4 hours. Rand Group recently reported that 98% of organizations say a single hour of downtime can cost over $100,000; doing the math reveals that those few few percentages can mean the difference between about $4,000 and nearly $3 million dollars.

Despite these scary numbers, some businesses have a tolerance for downtime, especially planned downtime such as maintenance. Businesses that still rely primarily on batch processing can often easily restart after an outage, and there’s usually significant leeway in completion times.

Redundancy Requirements by Tier

The other major difference between the tiers is in redundancy. Tier I data centers have a single path for power and cooling to the server equipment, with no redundant components. They typically do not have a backup cooling system or generator, so when they’re down—for maintenance, for instance—they’re completely down.

On the opposite end of the spectrum, a Tier IV data center is fully redundant. These data centers are outfitted with multiple cooling units, backup generators, power sources, and chillers. Even in the event of multiple equipment failure, they can continue to operate as normal.

Whereas a Tier IV data center can sustain a 96-hour power outage, a Tier I data center will shut down completely once the power goes out.

Every business needs to know how costly downtime will be for its specific bottom line, and the tier system is helpful in determining the type of data center offering that will provide just the right benefits. Tiers are an invaluable assistance for any business in thinking about exactly how much uptime it must have and exactly how much downtime will cost.

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About Blair Felter

As the Marketing Director at vXchnge, Blair is responsible for managing every aspect of the growth marketing objective and inbound strategy to grow the brand. Her passion is to find the topics that generate the most conversations.

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