Data Center Tiers
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
- An uninterruptible power supply (UPS) system
- expected to:
- help protect against human error
- not outages or disaster events
- have redundancy for chillers, pumps, UPS devices, and generators
- help protect against human error
- 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 |