A data center tier, or level, in other words, is used for differentiating key data center requirements, the focus being redundant components, cooling, load distribution paths, and other specifications. Each of these tiers can be defined precisely.
Traditionally, four tiers existed, but now a fifth one has also emerged featuring stronger requirements. Let’s quickly go through all these tiers to develop a basic understanding.
A Tier 1 data center is the simplest and the lowest level of all. The uptime level is around 99.671%, but compared to other tiers, it is a bit on the lower side because the data center features no or little redundancy. Thus, this means that power and cooling equipment has access to only a single path, implying a downtime of 28 to 29 hours on a yearly basis.
For small businesses with no complex requirements, a Tier 1 data center is a good choice, serving their needs pretty well.
A Tier 2 data canter has an uptime of 99.741% meaning that the total downtime hours in a year are not more than 22. Like a Tier 1 data center, the path for power and cooling is still one, but such a data center does comprise of some redundant components including a backup generator or cooling equipment, increasing reliability levels.
A Tier 3 data center is the choice of larger companies, featuring an uptime of around 99.982%. This means that the data center won’t go down for more than 1.6 hours in a year. Uptimes improve considerably for a Tier 2 data center because it features a sophisticated infrastructure and a high redundancy level, along with multiple paths for power and cooling. All the components are also connected to multiple power sources. If any of these fails, others can be utilized instead, so performance isn’t affected.
If maintenance and repairs are required, they can be done without shutting off the system itself. Also, certain measures are taken to protect the entire data center from a power outage.
Mega enterprises often select a Tier 4 data center, which exceeds the performance of all three tiers described above. The uptime percentages are as high as 99.995%, meaning that the data center will only suffer a downtime of 0.5 hours in a year. A Tier 4 data center also features 96-hour protection from the power outage and multiple redundancies to ensure that the system can normally perform even if a higher number of equipment fails.
A Tier 5 data center is a relatively newer trend, meeting all the requirements of a Tier 4 data center, along with additional ones. These include being able to perform without water, air pollutant detectors, securable server racks, and energy system monitor. A Tier 5 data center is usually preferred for local and renewable power projects.
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