Q. What is data center tiers? What is tier 1 data center? Which tier / level is the best for maximum uptime? A. Tier 1 to 4 data center is nothing but a standardized methodology used to define uptime of data center. This is useful for measuring: a) Data center performance b) Investment c) ROI (return on investment) Tier 4 data center considered as most robust and less prone to failures. Tier 4 is designed to host mission critical servers and computer systems, with fully redundant subsystems (cooling, power, network links, storage etc) and compartmentalized security zones controlled by biometric access controls methods. Naturally, the simplest is a Tier 1 data center used by small business or shops. Tier 1 = Non-redundant capacity components (single uplink and servers). Tier 2 = Tier 1 + Redundant capacity components. Tier 3 = Tier 1 + Tier 2 + Dual-powered equipments and multiple uplinks. Tier 4 = Tier 1 + Tier 2 + Tier 3 + all components are fully fault-tolerant including uplinks, storage, chillers, HVAC systems, servers etc. Everything is dual-powered. Data Center Availability According To Tiers The levels also describes the availability of data from the hardware at a location as follows: Tier 1: Guaranteeing 99.671% availability. Tier 2: Guaranteeing 99.741% availability. Tier 3: Guaranteeing 99.982% availability. Tier 4: Guaranteeing 99.995% availability.