Tier IV - Fault tolerant site infrastructure

The Uptime Institute fundamental classification of Tier IV states:

A fault tolerant data center has redundant capacity systems and multiple distribution paths simultaneously serving the site's computer equipment.

Typical Masterguard solution: Dual bus 2x (N+I) UPS system with dual static transfer switches

Summary

  • The principle of redundancy is extended further to include 2 x independent incoming supplies, 2 x (N+1) UPS systems and 2 x distribution.
  • HFC option ensures maximum fuse clearing capability and helps to ensure flexibility and maintainability of the system.
  • Load STS ensures that BOTH load power inputs remain powered even for load distribution fault.
  • UPS systems remain in synchronism to ensure load bus synchronism even during mains failures.
  • When either UPS is under maintenance the load still receives a protected AC supply from the alternative N+1 UPS with mains available as further back up.
  • Main and reserve auto-start generators or dual incoming AC supplies will satisfy the requirements for a second source of incoming AC supply.
  • The highest level of power availability for critical system loads.

 

Organisations will select Tier lV site infrastructure if they have an extremely high availability requirement for ongoing business or if there is a profound cost of disruption in the event of a data centre shutdown. These organisations will know the cost of a disruption in both financial terms and impact on market share. The cost of disruption makes the case for investment in high availability infrastructure a clear business advantage.

 

The performance confirmation test

A single worst case failure of any capacity system, capacity component or distribution element will not impact the computer equipment.

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

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

Complementary systems and distribution paths must be physically separated (compartmentalised) to prevent any single event from impacting on both systems or paths simultaneously.

 

The operational impact

The site is not susceptible to disruption from a single unplanned worst case event.

The site is not susceptible to disruption from any planned work activities.

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

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

Operation of the fire alarm, fire suppression, or Emergency Power Off (EPO) may cause a data centre disruption.