The Datacenter Tiers – What Are They?

By Donna Hemmert
AIS Network Vice President, Strategic Development

We’ve heard from some of our clients recently that there is some confusion about what the hosting tiers are and why they matter.  Well, we’d love to shed some light.

So, why are there tiers at all? The tiers help people understand the capabilities of a data center by describing the availability of data from the hardware at the datacenter. The Tiers are the requirements for “each level” of data center infrastructure. Overall, the higher the tier, the greater the availability.

Tier One

  • Basic site infrastructure with expected availability of 99.671%
  • Single non-redundant distribution path with non-redundant capacity components
  • Planned work and outages will require most or all of the site to be shut down

Tier Two

  • Meets or exceeds all Tier 1 requirements
  • Redundant site infrastructure capacity and single, non-redundant distribution path with expected availability of 99.741%

Tier Three

  • Meets or exceeds all Tier 1 and Tier 2 requirements
  • Concurrently maintainable site infrastructure with expected availability of 99.982%
  • Multiple independent distribution paths, but only one path required
  • Equipment is dual-powered & fully compatible with the topology of site’s architecture

Tier Four

  • Meets or exceeds all Tier 1, Tier 2 and Tier 3 requirements
  • Fault-tolerant site infrastructure with electrical power storage and distribution facilities with expected availability of 99.995%
  • Fault-tolerant with multiple, independent, physically isolated systems that provide redundant capacity components and multiple, independent, diverse, active distribution paths simultaneously serving the computer equipment.  Independently powered Cooling and power provided after infrastructure failure.

I hope that answers some of your questions.  Feel free to comment with questions.

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