What ensures the full functioning of systems during downtimes with a ready-to-go backup?

The correct answer, high availability, refers to systems and components that are continuously operational for a long period of time. High availability solutions are designed to minimize downtime and maintain system functionality, often through redundant systems that provide immediate failover capabilities. These solutions ensure that if one part of a system fails, another can take over with minimal interruption to services.

High availability typically involves using multiple servers or resources in a way that makes them work together seamlessly. This can include load balancers, clustering of servers, and failover systems that kick in automatically when a failure is detected. The main goal is to keep the system running and accessible to users, which aligns with the idea of having a 'ready-to-go backup' during downtimes.

While other options may seem relevant, they focus on different aspects of system management. Disaster recovery planning pertains to restoring operations after a catastrophic event. System redundancy also plays a role in ensuring availability but is typically a subset of high availability strategies rather than a standalone solution. Data protection is primarily concerned with the integrity and safety of data, rather than ensuring continuous system operation.