TIA-042 Data Center Classification

Tier descriptions include information like raised floor height, watts per square foot, and points of failure. “Need” or “N”, indicates the level of redundant components for each tier with N representing only the necessary system need.

Tier Level 1 – Basic: 99.671% Availability
• Single non-redundant distribution path serving the IT equipments
• Single path for power and cooling distribution, no redundant component (N)
• Susceptible to disruption from both planned and unplanned activity
• May or may not have a raised floor, UPS, or generator
• Annual downtime of 28.8 hours
• Must be shut down completely for perform preventive maintenance.

Tier Level 2 – Redundant Components: 99.741% Availability
• Fulfils all Tier 1 requirements
• Less susceptible to disruption from both planned and unplanned activity
• Single path for power and cooling disruption, includes redundant components (N+1)
• Includes raised floor, UPS, and generator
• Annual downtime of 22.0 hours
• Maintenance of power path and other parts of the infrastructure require a processing shutdown

Tier Level 3 – Concurrently Maintainable: 99.982% Availability
• Fulfils all Tier 1 & Tier 2 requirements
• Multiple independent distribution paths serving the IT equipments
• Multiple power and cooling distribution paths but with only one path active, includes redundant components (N+1)
• Enables planned activity without disrupting computer hardware operation, but unplanned events will still cause disruption
• Annual downtime of 1.6 hours
• Includes raised floor and sufficient capacity and distribution to carry load on one path while performing maintenance on the other

Tier Level 4 – Fault Tolerant: 99.995% Availability
• Fulfils 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
• Planned activity does not disrupt critical load and data center can sustain at least one worst-case unplanned event with no critical load impact
• Multiple active power and cooling distributions paths, includes redundant components ( 2(N+1), i.e. 2 UPS each with N+1 redundancy )
• Annual downtime of 0.4 hours