What method best ensures users have uninterrupted access to a heavily-used web application?

Load balancing is the best method to ensure users have uninterrupted access to a heavily-used web application because it distributes incoming user requests across multiple servers. By doing this, it prevents any single server from becoming overwhelmed with traffic, which can lead to slow response times or downtime. When the load is evenly distributed, the overall performance of the application improves, providing a seamless experience for users even during peak usage times.

Additionally, load balancing enhances fault tolerance. If one server fails, the load balancer can redirect traffic to other functioning servers, maintaining service availability. This redundancy built into the system is crucial for ensuring reliable access to web applications.

In contrast, disk mirroring safeguards data integrity by creating an exact copy of data on another disk but does not address the issue of managing user requests and application availability. A Redundant Array of Inexpensive Disks (RAID) improves data performance and redundancy at the storage level but does not handle web traffic distribution. A dynamic domain name system (DNS) can assist with resolving domain names to IP addresses but does not directly manage load or traffic distribution for web applications.

Therefore, load balancing stands out as the most effective solution for maintaining high availability and performance in heavily used web applications.