Which configuration represents Tier Four sites?

Tier Four sites are characterized by their high levels of redundancy and reliability in both infrastructure and data protection. The correct choice highlights that all computer equipment at Tier Four sites must have dual power inputs. This design feature is fundamental to Tier Four's requirements since it ensures continuous operation even in the event of a power failure or maintenance issues.

Having dual power inputs allows for true redundancy, meaning that if one power source fails, the other can take over seamlessly, thereby maintaining uninterrupted power for critical systems. This is essential for facilities that demand maximum uptime and resilience against any potential disruptions.

In contrast, the other configurations do not align with the stringent criteria outlined for Tier Four. For instance, having a single power input would create a single point of failure, which directly contradicts the redundancy principles of Tier Four. Additionally, basic cooling requirements wouldn't meet the advanced needs for robust climate control expected in such high-tier facilities.