A Tier IV data centre can withstand:

A Tier IV data centre is defined by the Uptime Institute as "Fault Tolerant." This means it is designed to withstand any single unplanned failure of a component or distribution path without impacting the critical IT load. This fault tolerance is achieved through multiple, independent, and physically isolated systems providing redundant capacity. Furthermore, a Tier IV facility is also "Concurrently Maintainable," meaning every component and distribution path can be taken offline for planned maintenance, repair, or replacement without causing any service disruption. Therefore, it can withstand both planned maintenance and any single failure.

C. A Tier IV design emphasizes automatic fault detection and response to prevent service impact, minimizing or eliminating the need for manual intervention for recovery.

D. A Tier IV facility has multiple, actively redundant distribution paths for both power and cooling to achieve fault tolerance. It is the antithesis of having no redundant paths.

1. Uptime Institute. (2021). Tier Standard: Topology. Section 2.0, "The Tiers," p. 8. The standard defines Tier IV as "Fault Tolerant Site Infrastructure" and explicitly states it allows for "any planned activity without disrupting the critical load" (Concurrent Maintainability) and can "sustain at least one worst-case, unplanned failure... with no impact to the critical load."

2. Rassouli, R., & Vali, A. (2012). A review on data center classification and tiers. International Journal of Computer Science and Network Security, 12(1), 108-112. This academic review paper summarizes the Uptime Institute's definitions, stating Tier IV provides fault tolerance against a single event and allows for concurrent maintainability. (Available via academic search engines).