Q&A Monday: Data Center Tiers



I am a small business owner looking to go with a cloud provider for our IT services.  Each of the vendors mentions their data center level, and I’ve tried doing research to figure out what these levels mean, but I can’t find anything describing them in plain English, can you help?

Vickie Downs
Watertown, NY



I will try my best to break the Data Center Tiers down into plain English for you.  The first thing you need to know when looking, is how mission critical are your servers, this will help you decide what data center is right for you.  Also it should be know that the higher the data center tier is, the more you are going to pay.
    OK, now to the explanation.  When you hear the term Data Center Tier (1 to 4) this is just a standardized methodology used to define availability (“uptime”) of data center. 

Tier Level Requirements
  • Single network infrastructure and connection to the internet
  • Non-redundant servers and power
  • Basic site infrastructure with expected availability of 99.671%
  • Meets or exceeds all Tier 1 requirements
  • Redundant site network, power or server with expected availability of 99.741%
  • Meets or exceeds all Tier 2 requirements
  • Multiple independent infrastructure 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%
  • Meets or exceeds all Tier 3 requirements
  • All cooling equipment is independently dual-powered
  • Fault-tolerant site infrastructure that includes generators and/or UPS and power outlets/breakers with expected availability of 99.995%

    As we can see from the chart above, Tier 4 data centers  are considered to be the most robust and less prone to failures.  Generally Tier 4 Data Centers are designed to host mission critical servers and computer systems, and they include fully redundant subsystems (cooling, power, network links, storage and servers) and have separated security zones controlled by bio-metric access controls methods. On the opposite end of this chart naturally is a Tier 1 data center used by small business or shops that don’t need or can’t afford the higher levels.

*Important Note*

Now people tend to brush off those availability numbers since they are only  .324% off from each other, but those number can add up to significant changes in downtime.  Below is the chart of allowed downtime in a given year at each tier level:

Tier Level Minutes of Downtime
1 1729.224 minutes
2 1361.304 minutes
3 94.608 minutes
4 26.28 minutes

If  you have any questions that you want Jim to answer, from business servers to home computers, drop him a line at me@jimguckin.com, and he’ll try to answer your question.  Check back every Monday for a new Question and Answer session, and also during the rest of the week for other technical insights.

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