Uptime Institute Tier Standard CertifiableUptime Institute

Data centre tier classification

The reference classification for data centres: Tier I to Tier IV, from no redundancy to fault tolerant. It translates a business availability requirement into a physical infrastructure requirement — and clarifies what a hosting provider is actually selling.

Official text

Who it applies to

Infrastructure managers
Hosting buyers
Recovery site auditors

Structuring points

Tier III enables concurrent maintainability; Tier IV tolerates an active fault
A high tier never removes the need for a second site: geography remains a risk factor
Certification covers design, construction or operations — three distinct objects

Data centre infrastructure topology and operations.