What’s the difference between a Tier 3 and a Tier 4 data center?

The Uptime Institute categorizes the data centers by four levels: Tier I, II, III and IV. These levels correspond to a certain number of guarantees on the type of hardware deployed in the data center to ensure redundancy.

Tier III

A Tier III data center offers 99.98% availability.
With this configuration, it is possible to manage maintenance periods without affecting the continuity of service on the servers. However, these data centers will not be protected from outages in the event of serious incidents occurring on different infrastructure components. In other words, the Tier III data centers do not have total modular redundancy.

Tier IV

The highest level of guarantee that a data center can provide, with 99.99% availability.
This data center category is fully redundant in terms of electrical circuits, cooling and network. This architecture can withstand even the most serious of technical incidents without server availability ever being affected.