A data center is a facility which comprised of a repository that contains a large number of computer systems and associated components like storage capacity, IT equipment, support infrastructure and operations staff to monitor the application uptime. Data center have typically classified into Tier 1 to Tier 4 to define uptime of the data center. This standardized methodology is used for measuring data center performance, investment, ROI.
Tier 1- Non redundant capacity components (single uplink and servers). It guarantees 99.671% availability.
Tier 2- Non-redundant capacity components involved in Tier1+ redundant capacity components. This Tier guarantees 99.741% availability.
Tier 3- It includes Tier 1+Tier 2+dual powered equipment and multiple uplinks. Tier 3 guarantees 99.982% availability.
Tier 4- All comprehensive features of Tier 1+Tier 2+Tier 3+ all components that are fully fault-tolerant including uplinks, storage, chillers, servers, etc. Everything is dual powered. It guarantees 99.995% availability.
Tier 4 data center is considered as the most robust and less vulnerable classification of data centers. Tier 4 is designed to host critical servers and computer systems with fully redundant subsystems (such as cooling, power, network links, storage capacity etc.) and compartmentalized security unit controlled by biometric access control method. Though, Tier 1 is a data center, simply used by small and medium type of businesses.