One thing about people who work in technology is that they love to classify and make lists. Lists can help to define problem and remind us of available solutions, and can be particularly helpful when attempting to make comparisons of different Data Center and Colocation facilities.
Several organizations publish standards which are used to make an attempt at allowing “apples to apples” comparisons between the infrastructure and uptime performance various data centers, since the users of data’s centers may have widely differing tolerance levels for downtime. If the cost of downtime for an organization running an application at a particular data center is high, the additional cost of a tier 3 or 4 data center will probably be easily justified. Conversely, if you are hosting your Rotary Club’s website, perhaps a Tier 4 Data Center might be a bit of overkill.
The two organizations in the United States that publish data center standards are the Telecommunications Industry Association (TIA) and the Uptime Institute. While the exact requirements of each group are different, both organizations classify a Tier One Data Center as having the least stringent uptime requirements, and a Tier Four Data Center as having the most stringent requirements. The cost of building and running a Tier 4 data center are significantly higher than a lower tier center.
The following are the Data Center Tier Standards published by the Uptime Institute:
Tier 1 Requirements
- Single non-redundant distribution path serving the IT equipment
- Non-redundant capacity components
- Basic site infrastructure with expected availability of 99.671%
Tier 2 Requirements
- Meets or exceeds all Tier 1 requirements
- Redundant site infrastructure capacity components with expected availability of 99.741%
Tier 3 Requirements
- Meets or exceeds all Tier 1 and Tier 2 requirements
- Multiple independent distribution paths serving the IT equipment
- All IT equipment must be dual-powered and fully compatible with the topology of a site’s architecture
- Concurrently maintainable site infrastructure with expected availability of 99.982%
Tier 4 Requirements
- Meets or exceeds all Tier 1, Tier 2 and Tier 3 requirements
- All cooling equipment is independently dual-powered, including chillers and heating, ventilating and air-conditioning (HVAC) systems
- Fault-tolerant site infrastructure with electrical power storage and distribution facilities with expected availability of 99.995%
The Uptime Institute’s tier system allows for the following minutes of downtime annually:
- Tier 1 (99.671% minimum uptime) (1729 minutes max downtime)
- Tier 2 (99.741% minimum uptime) (1361 minutes maximum annual downtime)
- Tier 3 (99.982% minimum uptime) (95 minutes maximum annual downtime)
- Tier 4 (99.995% minimum uptime) (26 minutes maximum annual downtime)
When you do the math, you will see that a Tier 1 data center user has a tolerance for downtime that is 66 times greater than a user who is willing to pay the additional cost of colocating in a Tier 4 data center space. Each user should perform a calculation of their own cost of downtime, and use that as a decision making tool when searching for data center space.