Redundancy and Failover

Correct Answer: Failover cluster

The correct answer is 'Failover cluster'. A data center with geographically dispersed redundant systems for disaster recovery indicates a setup where if one system fails, another system located at a different physical location instantly takes over, ensuring continuity in service. This is the functionality of a Failover Cluster. 'Load Balancer' is used to distribute network or application traffic across many resources (like servers) to enhance performance and reliability, but does not directly relate to disaster recovery. 'QoS system' (Quality of Service) is utilized to manage data traffic according to priority, bandwidth allocation, and other factors to improve service quality. It does not provide redundancy for disaster recovery'Firewall' is a security system that controls and monitors data traffic based on predetermined rules to protect networks from security threats. It also does not provide redundancy for disaster recovery.

Correct Answer: Uninterruptible Power Supply (UPS)

The best way to ensure that a server farm stays online during a power outage is by using an Uninterruptible Power Supply (UPS). This is a device that provides emergency power to a load when the input power source or mains power fails. In the context of a server farm, a UPS can provide temporary power which keeps the servers online during the outage. 'Power over Ethernet (PoE)' is useful for devices that are low voltage and are located where there is no electrical outlet, such as surveillance cameras, but it is not designed to supply the energy needs of a server farm. A 'Load Balancer' is used to distribute workloads across multiple computing resources, such as servers or clusters, which is irrelevant with power supply problem. 'Rack-mounted server' is just a way of mounting the servers and has no relation with server's electricity supply.

Correct Answer: High Availability (HA) solution

A High Availability (HA) solution is the correct answer because it refers to a type of system design aimed at ensuring an agreed level of operational performance, usually uptime, for a higher than standard period. High Availability systems are designed to be available during system failures, often by using redundancy of components or systems so if one fails, the other takes over. Content filtering, Firewall, and Network switch although are essential technologies in a networking environment, does not guarantee availability during system failures. Hence, they are not the appropriate answers for this question.