Which disaster recovery plan metric indicates how long critical functions can be unavailable before the organization is irretrievably affected?

The metric that indicates how long critical functions can be unavailable before the organization is irretrievably affected is known as maximum allowable downtime (MAD). MAD defines the upper limit of downtime that an organization can tolerate without sustaining severe damage, including financial loss, reputational damage, or loss of customers. This metric is essential for establishing a disaster recovery plan, as it helps organizations identify the threshold beyond which recovery efforts may no longer be effective, prompting them to prioritize resources and response strategies accordingly.

In contrast, other metrics, like recovery point objective (RPO) and recovery time objective (RTO), serve different purposes in disaster recovery. RPO focuses on the maximum age of the data that can be tolerated during a recovery, while RTO measures the time required to restore services after a disruption. Mean time to switchover (MTS) is concerned with the time it takes to switch operations from a primary to a backup site but does not specifically address the criticality of functions being unavailable. Understanding the difference between these metrics clarifies why MAD is the appropriate choice for indicating the duration of acceptable downtime relative to organizational impact.