Guide to Data Center Tier Classifications: Tier 1, 2, 3, and 4

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Data center tier specifications define the minimum performance, reliability, and quality a data center provides.

Understanding data center tier standards is key when choosing a hosting provider.

If you’re unsure whether the data center your hosting provider has all the features your business needs, look no further!

In this guide, we will cover everything about data center tier standards to help you make the right decision for your business.

What is the Data Center Tier Standard?

The data center tier standard is an internationally recognized standard for data centers that is defined by the Uptime Institute.

Essentially, the data center tier standard evaluates data centers based on reliability, quality, uptime, and overall performance.

Then, data centers are categorized into 4 tiers. The classification is based on their rating, with Tier 1 being the lowest-performing, and Tier 4 being the highest-performing tier.

However, the exact data center tier classification method used by the Uptime Institute isn’t publicly disclosed.

Nonetheless, most of the key factors that the Institute considers in the data center ratings are available to the public. These include:

  • Performance
  • Uptime and service availability
  • Security
  • Redundancy
  • Cooling and power infrastructure

The data center ratings are completely independent and objective, which means that data centers are evaluated based on their capabilities and performance alone.

Data Center Tier Ratings

Now, let’s overview each data center tier and its features.

Tier 1 Data Center

A Tier 1 data center has the lowest performance out of all data center tiers.

To be classified as a Tier 1 data center, a data center has to meet the following requirements:

  • Have a designated area for IT systems.
  • Use an uninterruptible power supply (UPS).
  • Use a dedicated cooling system that works beyond business hours.
  • Have an engine-generator for power cuts.

Generally speaking, Tier 1 data centers have a basic infrastructure, so they’re mostly used by hosting providers for shared hosting solutions.

Moreover, Tier 1 data centers typically offer few (if any) components that support redundancy. This means that such data centers aren’t reliable since they usually don’t offer backup options.

You should also keep in mind that Tier 1 data centers have to completely shut down for repairs and maintenance to prevent system failure.

Tier 2 Data Center

Similar to a Tier 1 data center, a Tier 2 data center uses a single power input and a single path for cooling.

For this reason, much like a Tier 1 data center, a Tier 2 data center doesn’t offer protection against unexpected disruptions.

Moreover, such data centers also need to be shut down for maintenance, repairs, and equipment replacement.

However, a Tier 2 data center has additional redundancy options, including:

  • Additional engine-generators.
  • Additional cooling systems and heat protection.
  • Chillers.
  • UPS modules.
  • Raised floors.
  • Energy storage.

Although Tier 2 data centers lack many features that Tier 3 and Tier 4 data centers offer, they are a more robust, secure, and reliable option than Tier 1 data centers.

Tier 3 Data Center

Unlike the previously mentioned data centers, a Tier 3 data center has multiple power inputs and paths for cooling.

Moreover, a Tier 3 data center doesn’t need to be completely shut down for maintenance because it has additional backup components. They kick in when the main components are being repaired.

In addition to all of the features of a Tier 2 data center, a Tier 3 data center must have:

  • An N+1 redundancy, “N” referring to the capacity needed to support the entire IT load, and “+1” referring to an additional backup element.
  • A backup component that ensures the data center operates during local and regional power outages.
  • The capacity to operate for a minimum of 72 hours after a power outage.

Although Tier 3 data centers offer superior redundancy compared to the first two tiers, they aren’t fully redundant as they can still be affected by unexpected external disruptions.

Tier 4 Data Center

A Tier 4 data center has the highest performance out of all data center tiers.

As such, to be classified as a Tier 4, a data center has to fulfill all the requirements mentioned above as well as ensure that:

  • All distribution paths are independent.
  • The data center is capable of operating for at least 96 hours after a power outage (local or region-wide).
  • Two cooling systems, two UPS modules, and two engine-generators to support all components.
  • An independent power supply that is not connected to any external sources.

Moreover, Tier 4 data centers must either have a 2N or 2N+1 redundancy model.

A 2N redundancy model means that the data center has an independent system on stand-by. If the primary system isn’t able to operate, an identical backup copy takes over the operations.

A 2N+1 redundancy model, on the other hand, offers double operational capacity and an additional backup component. The backup component continues the operations if the secondary system fails to operate.

As such, Tier 4 data centers offer uninterrupted availability and fault tolerance, making them the best option for most businesses.

Data Center Tiers By Uptime

Uptime refers to the percentage of time that a data center is available and working.

As such, uptime defines a data center’s reliability and quality.

Here’s how data center tiers compare by their uptime:

  • Tier 1 data center – uptime 99.671%, estimated maximum annual downtime 28.8 hours.
  • Tier 2 data center – uptime 99.749%, estimated maximum annual downtime 22.7 hours.
  • Tier 3 data center – uptime 99.982%, estimated maximum annual downtime 1.6 hours.
  • Tier 4 data center – uptime 99.995%, estimated maximum annual downtime 25 minutes.

What Data Center Tier is Best?

To choose the right web hosting provider for your business, it’s important that you research and consider the data center that they use.

This allows you to make an informed decision and ensures that your hosting provider meets your server security, service availability, and other hosting requirements.

As such, your best option is a hosting provider that uses Tier 3 or Tier 4 data centers, especially if your business owns large datasets.

That’s because these data center tiers offer the best data protection and efficiency with little to no downtime.

That being said, if the budget allows it, any business will benefit from choosing a hosting provider that uses a Tier 4 data center. That’s because Tier 4 data centers offer constant availability and fault tolerance.

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Guide to Data Center Tier Classifications: Tier 1, 2, 3, and 4

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