Tier II - Redundant capacity components site infrastructure
The Uptime Institute fundamental classification of Tier ll states:
A Tier II data centre has redundant capacity components and single non-redundant distribution paths serving the site’s computer equipment.
Typical Masterguard solution: Modular N+I parallel UPS system
Summary
- Redundancy is provided by a second UPS module running in parallel.
- This configuration exceeds the basic Tier ll requirement by enabling maintenance of each UPS module whilst the other is supporting the load, and therefore eliminates the need for total system shutdown for this purpose.
- Can be easily expanded to up to eight parallel modules for higher power or further levels of redundancy.
- Cost effective means of providing redundancy.
- If future requirements change, the system can be easily expanded or reduced and modules re-used elsewhere. Generators will normally meet the requirements for a second source of incoming AC supply.
Typical Masterguard solution: Centralised N+I parallel system
Summary
- System as per Modular Parallel System (diagram 2) but using a single “reserve static switch”, common to all UPS modules.
- Centralised static switch offers more flexibility in positioning UPS modules. Power cables to each UPS can be of different lengths because Vector Control UPS technology ensures correct parallel operation.
- Generators will normally meet the requirements for a second source of incoming AC supply.
Typical Masterguard solution: High fault capacity N+I parallel system
Summary
- System as per Centralised Parallel System (diagram 3) but with an additional High Fault Capacity (HFC) “reserve static switch”, that is common to all UPS modules.
- The HFC static switch can be removed for service and the system will still function as in diagram 2.
- Combines the advantages of the modular and centralized parallel UPS configurations with high fault clearing capability.
- The HFC configuration permits more flexibility by enabling the external static bypass switch to be maintained without taking the whole UPS system offline.
- Centralised static switch also offers flexibility in positioning UPS modules. Power cables to each UPS can be of different lengths because Vector Control UPS technology ensures correct parallel operation.
- Generators will normally meet the requirements for a second source of incoming AC supply.
Organisations will typically select Tier II infrastructure if they do not depend on real-time delivery of products or services for a significant part of their revenue stream, or are contractually protected from damages due to lack of system availability. Organisations may select Tier ll infrastructure if they have become burdened with impacts due to nuisance equipment outages associated with Tier l sites.
The performance confirmation test
A capacity component failure may impact the computer equipment.
A distribution path failure will cause the computer equipment to shut down.
The operational impact
The site is susceptible to disruption from both planned activities and unplanned events.
Redundant UPS modules and generators are required.
The site infrastructure must be completely shut down on an annual basis to safely perform preventive maintenance and repair work. Urgent situations may require more frequent shutdowns. Failure to perform this maintenance work increases the risk of unplanned disruption as well as the severity of the consequential failure.
Operation errors or spontaneous failures of site infrastructure components may cause a data centre disruption.