Data center tiers are the classification used to qualify the level of redundancy used in a data center. The official tier rating is regulated by the Uptime Institute. Tier certifications cover all aspects of the data center from power, cooling to construction.
Types of data center tiers
Data center tiers go from 1 to 4, tier 4 being the most redundant.
Tier 1 data centers have little to no redundancy or backup components. A tier 1 data center is expected to have a 99.671% rating of uptime, around 29 hours of downtime per year.
Tier 2 data centers have basic redundancy and have an uptime of 99.741%, which translates into 22 hours of downtime per year.
Tier 3 data centers are the most common. Tier 3 data centers have enough redundancy to maintain any component of the power or cooling infrastructure without affecting operations. Tier 3 data centers are expected to have at least 99.982% of uptime or 1.6 hours of downtime per year.
Tier 4 data centers are built to be 100% redundant. In a tier 4 data center, every component is doubled. From the power substations to the server rack, including cooling, there is always 2 times the necessary capacity to maintain operations (2N). Tier 4 data centers are expected to have 99.995% or 26.3 minutes of downtime per year, or less.
Are tier certifications important?
Unless your company absolutely needs its data center provider to have this certification, we do not consider the tier rating as a “must” when shopping for a data center provider. This certification costs a lot of money, that you will end up paying on your rent.
We consider it much more important to have a look at your provider’s power and cooling setup to ensure it’s redundant. We will always choose a provider with a better redundancy setup than one with an older or less redundant setup but that has the Uptime Institute paper.
Want to learn more about data centers and redundancy? Download our 2020 data center colocation buyer’s guide.