What is the difference between Tier 1, Tier 2, Tier 3, Tier 4 level of data center? Print

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What is a data center?

A data center is a facility that centralizes an organization’s IT operations and equipment, as well as where it stores, manages, and disseminates its data. Data centers house a network’s most critical hardware and software systems and are vital to the continuity of daily IT operations. Consequentially, the security and stability of data centers and their information is a top priority for organizations.

Datacenter generally includes redundant power supplies and networking, cooling and airflow, and fire safety regulations. A large data center uses as much power as a small town. Regardless of classification, an effective data center operation is achieved through a balanced investment in the facility and equipment housed. The elements of a data center break down as follows:


This represents the location or usable space, that is available for placing IT hardware equipment. Providing round-the-clock access to information makes data centers some of the most energy-consuming facilities in the world. A high emphasis is placed on design to optimize facility and environmental control to keep hardware equipment within the controlled temperature/humidity range.


Datacenter infrastructure includes UPS, Battery banks, computer room air conditioners (CRAC), heating, ventilation, air conditioning (HVAC) systems, and exhaust systems.

IT equipment:

Generally includes equipment for IT operations and storage of the company's data. This includes bare-metal servers, storage hardware, cables, and racks, as well as a variety of information security elements, such as firewalls.

Data centers are classified into four tiers based on the uptime institute's tier-based data center classification standard. This proprietary rating system begins with Tier I data centers, which are basically warehouses with power, and ends with Tier IV data centers, which offer 2N redundant power and cooling in addition to a 99.99% uptime guarantee.

A Tier III data center is concurrently maintainable, allowing for any planned maintenance activity of power and cooling systems without disrupting the operation of computer hardware in the data center. In terms of redundancy, Tier III offers N+1 availability. Any unplanned activity such as operational errors or spontaneous failures of infrastructure components can still cause an outage. In other words, Tier III isn’t completely faulted tolerant.

A Tier 4 data center is fault-tolerant, allowing for the occurrence of any unplanned activity while still maintaining operations. Tier 4 facilities have no single points of failure.

What is a Tier 1 data center?

Tier 1 data center requirements are generally utilized by small businesses and feature:

  • 99.671% Uptime
  • no redundancy
  • 28.8 hours of downtime per year.

What is a Tier 2 Data Center?

The benefits of a Tier 2 facility include:

  • 99.749% Uptime
  • Partial redundancy in power and cooling
  • Experience 22 hours of downtime per year

What is a Tier 3 Data Center?

Tier 3 data center specifications are utilized by larger businesses and feature:

  • 99.982% uptime (Tier 3 uptime)
  • No more than 1.6 hours of downtime per year
  • N+1 fault tolerant providing at least 72-hour power outage protection

What is a Tier 4 Data Center?

Tier 4 data center certification typically serve enterprise corporations and provide the following:

  • 99.995% uptime per year (Tier 4 uptime)
  • 2N+1 fully redundant infrastructure (the main difference between tier 3 and tier 4 data centers)
  • 96-hour power outage protection
  • 26.3 minutes of annual downtime.

Enterprises should question any Tier 4 claims by data center providers because it is difficult to get customers to pay the rates necessary to monetize the Tier 4 data center investment of roughly double that of a Tier 3 facility. 

All of SeiMaxim's core IT infrastructure is housed in Tier 4 data center to provide excellent services to our valued customers.

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