Data Center Tiers

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The Uptime Institute’s Tier Classification System describes four tiers with increasing requirements for maintenance, power, cooling, and fault tolerance.

• common measure of datacenters
• tiers are intended to map to business needs
  • not that one is better than another

Tier 1

A Tier 1 data center is the basic infrastructure required to support an organization that wants to conduct IT operations.

• requirements:
  • An uninterruptible power supply (UPS) system
    • for line conditioning and backup
  • Area to house IT systems
  • Dedicated cooling systems
  • Power generator for extended electrical outages
• expected to:
  • help protect against human error
    • not outages or disaster events
  • have redundancy for chillers, pumps, UPS devices, and generators
• likely to needs to shut down for maintenance

Tier 2

• provides more redundancy than Tier 1 facilities
• requires:
  • Generators and UPS devices
  • Chillers and cooling units
  • Pumps
  • Fuel tanks and other fuel storage
• intended to ensure critical operations are not interrupted due to planned maintenance

Tier 3

• known as a concurrently maintainable site infrastructure
• facility features both:
  • redundant capacity components of Tier 2
  • and multiple distribution paths where only a sole path is required to serve critical operations

Tier 4

• have independent and physically isolated systems providing redundancy and resiliency
  • at both component and distribution path levels
• are not disrupted if there is a planned or unplanned event
  • planned maintenance increases risk of outage for remaining redundant system
• designed around fault tolerance for components
  • a system failure will not result in failure of a service

Uptime Tiers

• uptime is considered in tiers
• Tier 1 allows up to 28.8 hours a year of downtime
• Tier 4 allows up to less than half an hour a year of downtime

Datacenter Tier	Uptime Percentage
Tier 1	99.671
Tier 2	99.741
Tier 3	99.982
Tier 4	99.995