Tier III - Concurrently maintainable site infrastructure

The Uptime Institute fundamental classification of Tier lll states:

A concurrently maintainable data centre has redundant capacity components and multiple distribution paths serving the site’s computer equipment. Generally, only one distribution path serves the computer equipment at any time.

Typical Masterguard solution: Redundant UPS module with dual static transfer switches

Summary

  • The requirement for multiple distribution paths is satisfied by fitting multiple electronic Static Transfer Switches (STS) so that the critical loads can benefit from two different AC supplies.
  • System output is maintained even if either one of the two incoming AC supply sources is shut down.
  • The UPS system remains in synchronism with the alternative supply source even if its own incoming supply is not available.
  • Alternative power paths ensure maintainability of the system.
  • Main and Reserve auto-start generators will normally meet the requirements for a second source of incoming AC supply.

 

Organisations selecting Tier lll infrastructure usually have high availability requirements for ongoing business or have identified a significant cost of disruption due to a planned data centre shutdown. These organisations are willing to accept the impact of disruption risk of an unplanned event. However, Tier lll is appropriate for organisations who expect the functionality requirements to increase over time. Some organisations design a Tier lll site so that it can be upgraded to Tier lV at a later date.

 

The performance confirmation test

Each and every capacity component and element of the distribution paths can be removed from service on a planned basis without causing any of the computer equipment to be shut down.

 

The operational impact

The site is susceptible to disruption from unplanned activities.

Planned site infrastructure maintenance can be performed by using the redundant capacity components and distribution paths to safely work on the remaining equipment.

In order to establish concurrent maintainability of the critical power distribution system between the UPS and the computer equipment, Tier III sites require all computer hardware have dual power inputs.

During maintenance activities, the risk of disruption may be elevated.

Operation errors or spontaneous failures of site infrastructure components may cause a data centre disruption.