The Telecommunications Industry Association (TIA) have published TIA-942 for Data Center Standards. The TIA-942 publication have tiered the Data Centers into the following four categories by the levels of Availability, Redundancy and Downtime:

Tier 1 Basic Data Center
  • 99.671% Availability

  • No redundancy

  • Single path for power and cooling distribution

  • May or may not have a raised floor, UPS, or generator

  • Annual downtime 28.8 hours

Tier 2 Redundant Components
  • 99.741% Availability

  • Redundant components

  • Single path for power and cooling distribution

  • Includes raised floors, UPS, and generators

  • Annual downtime 22.0 hours

Tier 3 Concurrently Maintainable
  • 99.982% Availability

  • Single path for power and cooling distribution

  • Redundant components

  • Includes raised floors, UPS and generators

  • Annual downtime 1.6 hours

Tier 4 Fault Tolerant
  • 99.999% Availability

  • Multiple active power and cooling distributions paths

  • Includes raised floors, UPS and generator

  • Multiple active distribution path