When choosing an IT solution for your business, be it a cloud or hosting service, it is of the utmost importance to consider the data centers where a provider’s servers are located. The speed of your web resources and the safety of your data depend on those servers’ reliability.
Data centers are classified according to reliability tiers: Tier I, Tier II, Tier III, and Tier IV.
In this article, we’ll talk about what this classification means, how to choose between data centers, and which criteria, other than reliability, are worth paying attention to.
It all began in 1993, when the Uptime Institute, along with companies responsible for maintaining the most important data centers in the United States, created a platform for sharing experiences.
This formed the basis of the criteria that the Institute developed for evaluating data centers. The classification itself was created in the 1990s.
The main goal pursued by the specialists of the Uptime Institute was to increase the reliability and resiliency of data centers.
The developed criteria serve as a guideline for those who build their own data centers. In order to assign a certain tier to a data center, the provider must be verified and receive a certificate from the Uptime Institute.
The classification makes choosing a provider much simpler for those who want to rent computing power. Reliability and availability are quite abstract concepts, so here they are in specific numbers.
The main parameters are the following:
99.995% availability—25 minutes downtime
99.982% availability—1.6 hours downtime
99.749% availability—22.7 hours downtime
99.671% availability—28.8 hours downtime
Note that Tier III and Tier IV have much less downtime. This is achieved due to the fact that these data centers don’t need to be stopped during repair and maintenance.
To determine which parameters a data center meets, many different factors are taken into account. The main ones are as follows:
This is the lowest level of reliability. In such data centers, a complete stop of work may happen both during maintenance and repair of equipment, as well as in case of technical failures.
There may be no backup systems at all, such as:
If there are such systems in the data center, then they are usually the simplest versions with many points of failure.
Also, in data centers of this tier, human error is very likely. There is very little protection from personnel errors.
The main difference between this level and Tier I is the availability of N + 1 redundancy of active equipment, which means that each active piece of equipment has one standby duplicate.
This also provides at least some (albeit minimal) protective measures against human error.
Despite this, Tier II data centers are still quite prone to downtime. To carry out scheduled maintenance work, they must be stopped.
Starting from this tier of reliability, data centers can be serviced without interrupting their work. This reduces downtime tenfold.
Like Tier II, data centers of the third level provide for N + 1 redundancy of active components.
But there’s more:
This is the maximum level of reliability. Like in Tier III, scheduled maintenance work in such data centers is carried out without stopping the systems. This data center is also able to withstand one crash.
This is achieved through 2(N + 1) redundancy, as there are two parallel elements that share the load, and each has a backup.
Moreover, this data center will have the following:
Tier IV surpasses the other tiers in all respects, so it would seem the obvious answer to choose the most reliable data center.
But the higher the availability, the more expensive the rent of computing power is. Therefore, the most powerful solution is not always the best from the budget point of view. When choosing, you need to focus on your needs first.
Tier I and Tier II data centers have a long downtimes per year, as there are planned outages. Therefore, renting computing power in such data centers is suitable only for those to whom periodic downtime will not be critical.
This is an option, for example, if your company is present only in a specific region and doesn’t work around the clock. Scheduled outages can then be carried out outside of working hours.
But if your business is present in countries with different time zones, and your services must be available 24 hours a day, it’s better to rent computing power only in Tier III or Tier IV data centers.
Tier III offers optimum reliability with a downtime of just 1.6 hours per year. Such a data center would be an excellent solution, for example, for hosting. Your web resources will be hosted on fault-tolerant servers at a lower cost than Tier IV. Tier IV is needed by those companies for which even an hour of downtime per year can bring losses. Choose this type of data center if you want to minimize the likelihood of server unavailability.
In addition to the tier of reliability, pay attention to the location of the data center. It should be close to the end users—the speed of content delivery depends on it. If all your visitors live in Europe, there’s no point in ordering servers in the USA.
And if you have an international company with customers all over the world, connect to a content delivery network (CDN) to deliver content anywhere in the world as quickly as possible.
Before renting computing power, be sure to check the provider’s reputation. Read reviews and see what the media says about this or that vendor. Perhaps you’ll stumble upon information that sheds some light on whether or not a company actually provides a resilient infrastructure.
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Read more about hosting and cloud features and their differences in our article, “Cloud vs hosting: which should you choose?”.
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