[Image: This Chart Illustrates Tier Similarities and Differences. Image
Courtesy of The Uptime Institute]
A four tier system that provides a simple and effective means for identifying
different data center site infrastructure design
topologies. The Uptime Institute's tiered classification system is an industry
standard approach to site infrastructure functionality addresses common
benchmarking standard needs. The four tiers, as
classified by The Uptime Institute include the following:
- Tier 1: composed of a single path for power and cooling
distribution, without redundant components, providing 99.671% availability.
- Tier II: composed of a single path for power and cooling
distribution, with redundant components, providing 99.741% availability
- Tier III: composed of multiple active power and cooling
distribution paths, but only one path active, has redundant components, and
is concurrently maintainable, providing 99.982% availability
- Tier IV: composed of multiple active power and cooling
distribution paths, has redundant components, and is fault tolerant,
providing 99.995% availability.
Tier I sites will have computer power distribution and cooling but may not
have raised floors, UPSes, or engine generators. The critical load on these
systems is up to 100 percent of N. Even with a UPS or generator, they likely are
single-module systems and have many single points of failure. The infrastructure
should be completely shut down on an annual basis to perform preventive
maintenance and repair work. Urgent situations may require more frequent
shutdowns. Tier IV data centers have all the bells and whistles; everything
needed to keep them running without ever shutting down for maintenance, no
matter what happens.
[Tier examples courtesy of
Processor: How's & Why's Of Data Center Tiers]
