Data center tiers is a classification about the level of service that a data center offers. Every data center comes with a tier ranking and is classified as Tiers 1,11,111 and IV. It includes everything from uptime commitment to the physical infrastructure like power backups, cooling systems, redundancy level etc.
Tier 1 data center is the simplest and most affordable with no assured commitments of redundancy in components or uptime. It offers single path for power and cooling systems with no proper power and cooling backup. Tier 1 data center has an uptime of 99.671% with annual downtime of 28.8 hours.
Tier 11 data center also offers a single path for power and cooling but has some redundancy in infrastructure with power and cooling backup. It is more reliable than Tier 1 and has an uptime of 99.741% and a downtime of 22.68 hours in a year.
Tier 111 comes with multiple path power and cooling solutions.It has the capability to run on the redundant resources at times of maintenance and any hardware replacement. The uptime commitment is of 99.982% and a downtime of 1.6 hours.
Tier IV is the strongest, meets all the requirements of Tier 1, 2 and 3 and offers uptime guarantee of 99.995% and downtime of 26 minutes in a year.