A data center is a complex, multi-technical infrastructure: server rooms, network rooms, telecommunications rooms… Not forgetting the power distribution system, generators, fire safety system, air-conditioning system…
Last but not least, a data center is a highly complex industry, requiring constant attention to achieve and maintain the highest levels of security and availability.
IT outsourcing has become a matter of course for many companies. Hosting your IT in a data center means you benefit from top-quality infrastructure, enhanced security and high availability.
So how are data centers classified?
Uptime Institute: Classification of data centers
Uptime Institute is the founding company of the datacenter classification system, established over 25 years ago. It is the sole provider of these certifications.
This independent organization classifies data centers into four levels called ” Tier ” to evaluate different data center facilities. The levels are progressive, so that each level integrates the requirements of the lower levels.
The aim of this classification system is to make it easier for users to identify the data center that will meet their availability and security requirements.
Tier I – Basic datacenter
Tier I certified data centers represent the lowest category awarded by the Uptime Institute.
This level corresponds to a data center witha single power supply and climate control, with no redundancy.
It offers an availability rate of 99.671%, with an average of 28.8 hours of downtime per year.
A Tier I datacenter requires downtime for maintenance. Faults also stop site operation.
Tier II – Partial redundancy
Tier II-certified data centers represent a slight improvement over a Tier I facility.
The data center features partial redundancy and a single power and cooling path.
Certain maintenance operations or breakdowns can lead to downtime.
The availability rate of a Tier II data center is 99.741%, with an average of 22 hours of downtime per year.
Tier III – Concurrent maintenance
A Tier III data center comprises several electrical circuits for power and cooling distribution, with N+1 redundant components. However, only one circuit is active ( active/passive mode distribution).
A Tier III data center offers an availability rate of 99.982%, and suffers an average of 1.6 hours of downtime per year.
A Tier III datacenter remains vulnerable to certain maintenance or breakdowns that may require the infrastructure to be shut down.
Tier IV – Fault tolerance
A Tier IV data center consists of several electrical circuits for power and cooling distribution, with physically compartmentalized and fully redundant 2N components. All circuits operate in active/active mode.
A Tier IV data center supports fault tolerance: the environment will not be affected by any interruption of planned or unplanned events, offering an availability rate of 99.995%, with an average downtime of 0.8 hours per year.
Zero single point of failure: No failure, error or maintenance can stop the system.
PLEASE NOTE:
As part of the Tier IV certification process, the Uptime Institute requires the datacenter to have two totally independent sources of power generation and distribution.
Power from an external electricity supplier is only a source of savings (not resilience).
Internal production is taken into account by the Uptime Institute if the datacenter has internal production facilities (e.g. production generators, not backup generators).
TIER LEVELS ACCORDING TO UPTIME INSTITUTE | TIER I | TIER II | TIER III | TIER IV |
---|---|---|---|---|
Energy sources Electric (Generator, Gas heater, Cooling unit…) |
1 system | 1 system | 1 shared system | Redundant |
Electrical and air conditioning |
Simple | Simple | Liabilities/Assets | Assets / Assets |
Redundancy of system components electrical / Air conditioning |
N | N+1 | N+1 | 2N |
Continuous cooling | no | no | Depends on density load |
yes |
Compartmentalized zones | no | no | no | yes |
Single fault tolerance | no | no | no | yes |
The system enables parallel maintenance to production |
no | no | yes | yes |
Availability rate Annual computer system downtime |
99,67% 28,8 H |
99,75% 22 H |
99,98% 1,6 H |
99.995% and more 0,8H |