It has happened to nearly every hosting customer at some point. You’re researching a host and visiting their “Why Us” page or some other page with information about the company. There they talk about how they run a “Tier 3″ or “Tier 2″ data center with no explanation about what that means.

Though hosting geeks instantly understand what the tier system means, even hosts aimed at every day users, such as Media Temple, which talks about being a “top tier data center” and IX Web hosting, which mentions being a “tier 3” datacenter, use the terminology as well, understandably confusing many.

However, the data center tiers are actually very easy to understand and, even if you don’t fully understand what the tiers mean, you can certainly understand what to look for and what is “good” when seeking out hosting.

Without further ado, here’s your primer in the data center tiers and what you should be looking for.

Tearing Up the Tiers

The datacenter tier system was actually developed and is currently certified by the Uptime Institute, a think tank and services company that specializes in improving data center reliability.

The system works around a score given according to how redundant the data center is and how much uptime it can guarantee. Using the tier system, a “Tier 1″ data center is the lowest and least reliable and a “Tier 4″ is the best.

However, each tier comes with a set of specifications that it must meet in order to be certified at that level.

1. Tier 1: Has no redundancy at all including for power and for components. Guarantees a reliability of 99.671%.
2. Tier 2: Meets the requirements for Tier 1 and also adds in redundant components, increasing reliability to 99.741%.
3. Tier 3: Meets the requirements for Tier 2 and also has multiple power and cooling sources, though only one is active at a time, and the redundant components now concurrently maintainable. Uptime increases to 99.982%
4. Tier 4: Meets the requirements for Tier 3 but now everything is dual-powered, including the cooling and and the site is built to be fault-tolerant and compartmentalized. Uptime now reaches 99.995%.

However, the details aren’t very important, what is important is that the higher the number, the better the data center and the better the uptime it can guarantee. A Tier 3 data center is generally thought to be very good and a Tier 4 one is considered acceptable for mission-critical applications. Tier 1 and Tier 2 sites typically don’t bother with certification.

What About Bandwidth Tiers?

In addition to describing tiers for their data centers, many hosts, such as Servint, which hosts this site, goes on to talk about getting their bandwidth from “Tier 1″ sources.

Unlike the data center tiers, there is no certification body for bandwidth tiers and, to make matters more confusing, the numbering system is reversed with 1 being the best out of a scale of 1-3.

A Tier 1 bandwidth provider is simply a provider that operates “settlement free” or doesn’t pay other providers for its bandwidth. This is often referred to as “peering”. A Tier 2 provider peers with some networks but pays for access to other providers. A Tier 3 providers solely purchase their access from a third party.

Generally speaking Tier 1 bandwidth providers are considered the best as they are close to the “center” of the Internet and are considered to be faster and more reliable. Most hosts, however, have multiple bandwidth providers for redundancy, often times mixing tiers.

All in all, the key to remember is that, with bandwidth providers, the lower the tier number the better, unlike data center tiers with the higher the number being the better.

Bottom Line

How much does all of this matter? Really not all that much. As you can see from the relative uptimes provided by the different tiers for datacenters, one does not get significantly improved uptime at a Tier 3 vs. a Tier 2 and one is unlikely to find a reasonably-priced host at a Tier 4 data center, those are usually reserved for cases where extreme uptime is a requirement and few hosting data centers operate at a Tier 1 level.

Furthermore, the tier of the bandwidth provider matters less than the redundancy and speed. It is far more important that the host have multiple connections and adequate high-speed bandwidth than it all be from Tier 1 providers.

In short, while this information can be great, its usefulness in determining which host you should use is minimal. As discussed in the post about geography and hosting, there are many other important factors in determining the speed and reliability of a host not discussed in these tier ratings.

So don’t be alarmed if your host doesn’t provide this information, many hosts don’t, but now you’ll understand what it means if they do.

(Thanks to pzado for the image)

Tags:   bandwidth • certification • data center • datacenters • tiers • uptime institute