During an IT disaster recovery test, what issue should be of greatest concern to the IS auditor?

The issue of defective or non-working backup systems is of utmost concern during an IT disaster recovery test, as it directly impacts the organization's ability to recover from an actual disaster. The primary goal of a disaster recovery plan is to ensure that systems can be restored and made operational after a disruptive event. If backup systems are found to be defective during testing, it raises significant doubts about the reliability and effectiveness of the recovery process. This could result in prolonged outages, data loss, or even total failure to restore critical services when they are needed most.

While the other concerns mentioned may impact the overall disaster recovery testing process, they don't possess the same level of criticality as system integrity and functionality. For example, testing only essential systems could potentially leave other key components unprepared, and delays in shutting down the original site can complicate recovery but are more related to procedural efficiency than to the fundamental ability to recover systems. Similarly, having the same employees conduct tests yearly may lead to familiarity and complacency, but it does not inherently compromise the technical capabilities of the backup systems. Therefore, ensuring the operational status of backup systems is the priority that directly relates to the organization's resilience in the face of a disaster.