We recently published a blog post about important questions to ask your cloud provider. One of these questions related to certifications for a data center, specifically what tier the data center has achieved. What is the tier classification system?
What are the Tiers?
The Uptime Institute created the standard Tier Classification System to consistently evaluate various data center facilities in terms of potential site infrastructure performance, or uptime. The Tiers (I-IV) are progressive; each Tier incorporates the requirements of all the lower Tiers.
A Tier I data center provides dedicated site infrastructure to support information technology beyond an office setting. Tier I infrastructure includes a dedicated space for IT systems; an uninterruptible power supply (UPS) to filter power spikes, sags, and momentary outages; dedicated cooling equipment that won’t get shut down at the end of normal office hours; and an engine generator to protect IT functions from extended power outages.
Single non-redundant distribution path serving the IT equipment
Non-redundant capacity components
Basic site infrastructure with expected availability of 99.671%
Tier II facilities include redundant critical power and cooling components to provide select maintenance opportunities and an increased margin of safety against IT process disruptions that would result from site infrastructure equipment failures. The redundant components include power and cooling equipment such as UPS modules, chillers or pumps, and engine generators.
Meets or exceeds all Tier 1 requirements
Redundant site infrastructure capacity components with expected availability of 99.741%
A Tier III data center requires no shutdowns for equipment replacement and maintenance. A redundant delivery path for power and cooling is added to the redundant critical components of Tier II so that each and every component needed to support the IT processing environment can be shut down and maintained without impact on the IT operation.
Meets or exceeds all Tier 2 requirements
Multiple independent distribution paths serving the IT equipment
All IT equipment must be dual-powered and fully compatible with the topology of a site's architecture
Concurrently maintainable site infrastructure with expected availability of 99.982%
Tier IV site infrastructure builds on Tier III, adding the concept of Fault Tolerance to the site infrastructure topology. Fault Tolerance means that when individual equipment failures or distribution path interruptions occur, the effects of the events are stopped short of the IT operations.
Meets or exceeds all Tier 3 requirements
All cooling equipment is independently dual-powered, including chillers and heating, ventilating and air-conditioning (HVAC) systems
Fault-tolerant site infrastructure with electrical power storage and distribution facilities with expected availability of 99.995%
Data center infrastructure costs and operational complexities increase with Tier Level, and it is up to the data center owner to determine the Tier Level that fits his or her business’s need. A Tier IV solution is not “better” than a Tier II solution. The data center infrastructure needs to match the business application, otherwise companies can overinvest or take on too much risk.
Uptime Institute recognizes that many data center designs are custom endeavors, with complex design elements and multiple technology choices. As such, the Tier Classification System does not prescribe specific technology or design criteria. It is up to the data center owner to meet a Tier Level in a method that fits his or her infrastructure goals.
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