Weighing the Pros and Cons of Data Center Tiers

Data center tiers can be used to distinguish different types of facilities, but it is important to understand the ranking system’s limitations.

Christopher Tozzi, Technology Analyst

January 24, 2024

4 Min Read
Weighing the Pros and Cons of Data Center Tiers

All data centers do the same basic thing – provide a space for hosting IT infrastructure. So how do you know if one data center is ‘better’ than another? One way is to look at data center tiers.

The data center tiering system classifies data centers based on their reliability. The higher a data center's tier, the more uptime you can expect from the facility.

That said, the data center tiering system has its flaws. Tier certifications are arguably the most straightforward way to compare the value of different data centers, but it's critical to recognize their limitations, too.

Keep reading for a look at what data center tiers mean, as well as how much stock to assign to tiers when comparing data center facilities.

What Are Data Center Tiers?

Data center tiers are classification levels assigned to data centers based primarily on their reliability. There are four tiers:

  • Tier 1: Tier 1 data centers lack substantial backups or redundant systems. They deliver the lowest level of uptime.

  • Tier 2: Tier 2 data centers offer limited redundancy, resulting in somewhat higher uptime than Tier 1 facilities but still posing a risk of significant downtime.

  • Tier 3: Tier 3 data centers have redundancies for key systems to reduce the risk of downtime due to major equipment failures.

  • Tier 4: Tier 4 data centers are designed to be completely fault-tolerant, such that no single system failure will cause downtime. This is the most reliable data center tier.

Related:10 Key Data Center Acronyms Shaping the Industry in 2024

The more redundancy that data center designers and operators build into a facility, the higher its tier rating.

Who Assigns Data Center Tiers?

Data center tiers are assigned by the Uptime Institute, an advisory organization that develops standards and performs assessments related to uptime and reliability in the IT industry.

A data center operator can request a tier assessment from the Uptime Institute, which then reviews the facility and determines which tier best corresponds to it.

At least, that's the way that data center tiering is supposed to work. In practice, some data center operators may describe their facilities as "Tier 3" or "Tier 4" without actually undergoing an official assessment.

Indeed, some data centers go as far as to assert that they are "Tier 5" facilities, even though the Uptime Institute doesn't officially recognize a Tier 5 data center classification. Tier 5 certification is something data center operators simply assign themselves, which means it doesn't hold much value in practical terms.

So, before assuming that a given data center conforms with the tier level it claims, check whether the facility has been formally reviewed.

Related:Retrofitting, Refurbishment, and ROI for Legacy Data Centers

The Pros and Cons of Data Center Tier Certifications

The data center tiering system is one of those things that's easy to love and hate at the same time.

It's easy to love because it's one of the only classification systems that provides a straightforward way of comparing how reliable one data center is likely to be relative to another.

Without data center tiers, the only way to evaluate reliability would be to conduct detailed assessments of each facility. But the tiering system means that the Uptime Institute does this work, helping businesses looking for a data center to compare their options in a simple way.

On the other hand, data center tier certifications are subject to a variety of potential drawbacks:

  • Although the Uptime Institute provides an overview of how it determines tiers, its exact formula is not public, so the tiering certifications are not completely transparent.

  • The tiers focus on reliability and uptime expectations, not other data center characteristics that businesses might care about (such as how sustainable a facility is).

  • Tier certifications don't guarantee a specific level of uptime or provide compensation if data centers fail to achieve the uptime expected based on their tier ratings. The tiers simply provide guidance on how much uptime to expect based on the way a data center is designed.

  • The tier levels don't factor in considerations like how prone a data center is to natural disasters based on its location. They are based only on the availability of backup and redundant systems.

  • As noted above, some data center operators claim to have achieved a certain tier level even though they did not undergo an actual assessment. In this sense, the data center tier system can be abused for marketing purposes in ways that mislead buyers.

How Much Stock to Put in Data Center Tier Ratings

In short, data center tier certifications are a useful way of gauging the amount of uptime that data centers are likely to provide. But they offer little insight beyond uptime expectations, and at the end of the day, they don't guarantee specific levels of uptime or anything else.

Thus, while data center tiers are one factor to look at when selecting a facility, don't obsess over tier certifications – especially not in cases where a data center hasn't been assessed by a neutral party to determine which tier it conforms with.

About the Author(s)

Christopher Tozzi

Technology Analyst, Fixate.IO

Christopher Tozzi is a technology analyst with subject matter expertise in cloud computing, application development, open source software, virtualization, containers and more. He also lectures at a major university in the Albany, New York, area. His book, “For Fun and Profit: A History of the Free and Open Source Software Revolution,” was published by MIT Press.

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