Data Centers and the Four-Tier System
A Data centre or data center is defined as “a centralized repository, either physical or virtual, for the storage, management, and dissemination of data and information organized around a particular body of knowledge or pertaining to a particular business.” It is a facility that houses the computer systems, data storage systems, telecommunications, data connectivity, equipment housing and support, electrical power distribution, backup power systems, back up data communication connections, environmental systems, fire suppression systems and security systems. For any business organization, smooth IT operations are crucial in order to achieve uninterrupted business continuity. Hence, data centre is one of the most important parts of a business as it helps to keep the business running smoothly and efficiently.
The Telecommunications Industry Association published the Telecommunications Infrastructure Standard for Data Centers (ANSI/TIA-942) in 2005 that was later amended in 2008 and 2010 (TIA-942: Data Center Standards Overview) to specifically address the data center infrastructure. It divided data centers into four levels called tiers to define uptime of data centers. The TIA-942 Data center standards provide architectural, electrical, security, mechanical and telecommunications recommendations for each tier. This four-tier system provides a simple means to understand the infrastructure design topologies of data centers and the availability of data from the hardware at a location. A leading service provider with several data centers in India has a world-class TIER 3+ ISO certified infrastructure across all data centers with 99.99% uptime. Let’ look at data center tiers in detail.
Tier 1 – Basic Site Infrastructure
* Guarantees 99.671% availability
* Vulnerable to disruptions from both planned and unplanned activity
* Single path for power and cooling distribution
* May/may not have a UPS, raised floor or generator
* 3 months for completion
* 28.8 hrs of annual downtime
* Preventive maintenance is possible only after a complete shutdown
Tier 2 – Redundant Components Site Infrastructure
* Guarantees 99.741% availability
* Less vulnerable to disruptions from both planned and unplanned activity
* Single path for power and cooling distribution and includes redundant components (N+1)
* Has raised floor, UPS and generator
* 3 to 6 months for completion
* 22.0 hours of annual downtime
* Processing shutdown necessary for the maintenance of power path and other parts of the infrastructure
Tier 3 – Concurrently Maintainable Site Infrastructure
* Guarantees 99.982% availability
* Enables planned activity but susceptible to unplanned activity
* Multiple power and cooling distribution paths but only one path active and includes redundant components (N+1)
* 15 to 20 months for completion
* 1.6 hours of annual downtime
Tier 4 – Fault Tolerant Site Infrastructure
* Guarantees 99.995% availability
* No load impact during planned activity and can sustain at least one worst-case unplanned event
* Multiple active power and cooling distribution paths and includes redundant components 2 (N+1)
* 15 to 20 months for completion
* 0.4 hours of annual downtime
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