Continuous availability specifically during hardware maintenance requires that individual components can be taken offline, serviced, or replaced without interrupting overall service, which is exactly what redundant, fault-tolerant, and hot-swappable component design enables: redundant components ensure a standby or peer unit continues serving the workload while another is being maintained, and hot-swappable design allows physical replacement or servicing without powering down the surrounding system. This directly addresses the operational requirement of performing maintenance while services remain continuously available, making it the most appropriate activity among the options given. A data archiving solution (A) is unrelated to hardware maintenance or service continuity during that maintenance; archiving addresses long-term retention of inactive data, not operational uptime during servicing activities. Establishing guidelines based on defined availability levels (C) is a planning and governance activity that sets targets and expectations, but does not itself provide the technical mechanism that keeps services running while maintenance is performed. Monitoring availability (D) provides visibility into whether components are up or down, which is valuable operationally, but monitoring alone does not prevent an outage during maintenance; it only observes the outcome rather than architecting around it. Redundant, hot-swappable design is the correct, direct answer.

Reference topic: Fault Tolerance Techniques - Redundancy for Continuous Availability During Maintenance.