How do Data centers stack up?
When comparing data centers, it is common to put facilities in a Tier system. The Uptime Institute maintains this standard. It defines 4 levels that describe the quality and reliability you can expect from a data center. Of course, these levels can’t predict acts of nature or other disasters. Even so, they offer a clear look at the care and craftsmanship behind a facility’s construction.
When shopping for a data center, it’s critical to look at the levels of advertised service and what they mean. This standard has existed since 2006, so if a facility predates that year, assume it wasn’t built to spec.
The 4 Data Center Tiers, Explained
Tier 1
Tier 1 has a single path of service in the infrastructure, meaning there is no backup if a hardware problem occurs with power or networking equipment. This also applies to cooling equipment and other mission-critical infrastructure which requires maintenance. This maintenance is factored into how much downtime you will experience.
Advertised downtime should be around 99.6%. This estimate allows for a day or two of downtime each year, or a couple hours a month. Keep in mind that the nature of this design lends itself well to unforeseen disasters. Without any redundancy for maintenance, it is likely that other corners were cut as well. Not recommended!
Tier 2
Tier 2 has a similar infrastructure with some redundancies in place. This is good for planned maintenance, but is still pretty limiting from an engineering perspective. The distribution path of power and networking are still not redundant, meaning that the level of service is not a great deal better.
Advertised downtime should be around 99.741%. Regular downtime at this level is a minimum of 1 day per year, which translates to at least half an hour per week.
Tier 3
Tier 3 begins to demonstrate a viable facility for mission-critical colocation. Multiple distribution paths for connectivity are present, limiting a single point of failure. This causes maintenance at this facility to be seamless and non-disruptive.
Advertised downtime should be around 99.982%. Downtime is minimal, less than one hour per year, meaning about half a minute per month. This sounds great on paper, but there are still serious problems which can arise. Cooling equipment does not have redundant components, which means that during maintenance the facility can become unexpectedly hot, which could cause instability in your infrastructure. Also, power storage and distribution is not fault tolerant in a Tier 3 facility. This can mean power complications that could cause your hardware to power down or even absorb damage.
Tier 4 (Tier IV)
Tier 4 is the highest level of service a data center can offer. Redundancies deter any type of outage, including redundant components inside redundant appliances for power, networking, and cooling. This allows for absolute minimum downtime, even during a worst-case scenario of an unplanned failure.
Advertised downtime should be around 99.995%. You can expect less than 20 minutes of downtime during an entire year, most likely spread out during non-business hours and barely noticeable.
