What is the best method to ensure high availability for a mission-critical application on a single server?

To ensure high availability for a mission-critical application on a single server, configuring failover clustering is the most effective method. Failover clustering allows multiple servers to work together as a single system to provide continuous availability. If one server (also known as a node) fails, the application can automatically switch over to another server in the cluster, which minimizes downtime and risk of disruption to users.

This method is especially powerful for mission-critical applications, as it enables seamless failover without significant interruption. By using additional hardware resources, such as a second server, organizations can create redundancy and maintain service continuity even in the event of hardware or software failures.

The other options, while beneficial in their own contexts, do not provide the same level of high availability. Adding multiple disks and configuring RAID 5 improves data reliability and redundancy but does not protect against server failures. Similarly, adding an additional NIC configured as standby enhances network reliability but does not address the overall availability of the server itself. Moving the application to another server may provide more resources, but it does not inherently offer a solution for high availability on the original server. Thus, failover clustering is the optimal choice for achieving high availability in this scenario.