The most vital departure from the Tier Standard found in most data facilities is summarized as inconsistent solutions. Frequently, a data facility will have a fault tolerant electrical system designed using the Tier IV standard, but will utilize a Tier II mechanical system that can’t be maintained unless facility operations are interrupted. This results in an overall Tier II rating.
Mechanical systems typically fail concurrent maintenance criteria due to inadequate coordination between the quantity and location of isolation valves within the chilled water distribution path. Another common oversight is branch circuiting of mechanical components, which results in having to shut down the entire mechanical system to perform electrical maintenance. Furthermore, facility cooling is impacted If more than the redundant number of chillers, towers, or pumps is de-energized for electrical maintenance.
Electrical systems often fail to achieve Tier III or Tier IV standards due to design decisions made in the UPS and the critical power distribution path. UPS configurations that utilize common input and output switchgear are nearly always unmaintainable without critical environment outages and will fail the Tier III requirements even after spending many hundreds of thousands of dollars. Topologies that utilize static transfer switches in the critical power path for single-corded IT devices will likely fail not only the fault tolerance criteria but also the concurrent maintenance criteria.
Consistent application of standards is critical to achieve an integrated solution for a specific data center. Often, when the electrical and mechanical infrastructures are defined and the facility operations are established, there is a growing degree of inconsistency in the solutions incorporated in a facility. An investment in one segment must be met with a similar investment in each of the other segments if any of the elements in the combined overall solution are to have the desired effect on availability. A well-executed data facility master plan or strategy should systematically meet the entire spectrum of facility requirements.
Want to better understand the Tier Standard Classifications? Read our article: Data Center Tiers Explained
| Data Center Tier Requirements Summary | ||||
|---|---|---|---|---|
| Tier I | Tier II | Tier III | Tier IV | |
| Minimum Capacity Components to Support the IT Load | N | N + 1 | N + 1 | N After any failure |
| Distribution Paths - Electrical Power Backbone | 1 | 1 | 1 Active + 1 Alternate | 2 Simultaneously Active |
| Critical Power Distribution | 1 | 1 | 2 Simultaneously Active | 2 Simultaneously Active |
| Concurrently Maintainable | No | No | Yes | Yes |
| Fault Tolerance | No | No | No | Yes |
| Compartmentalization | No | No | No | Yes |
| Continuous Cooling | No | No | No | Yes |
Source: Uptime Institute®, a division of The 451 Group. "Data Center Site Infrastructure Tier Standard: Topology©" Uptime Institute, www.uptimeinstitute.com/resources/asset/tier-standard-topology. Accessed 11 December, 2019