N10-009 Question 218
Single answerDR metrics: Recovery point objective (RPO), Recovery time objective (RTO), Mean time to repair (MTTR), Mean time between failures (MTBF)A healthcare clinic is reviewing its disaster recovery plan for a patient scheduling system. Management states that after an outage, the system must be restored within 2 hours, and the clinic can tolerate losing no more than 15 minutes of appointment data entered before the failure. During a review meeting, a technician says, "Our storage array has an MTBF of 200,000 hours, so that means we can recover the application within the required window." Which statement best addresses the technician's misunderstanding?
- A
MTBF measures the average time between device failures, but RTO defines how quickly the service must be restored after an outage.
- B
MTBF measures the maximum tolerable data loss, while RPO defines the expected hardware lifespan.
- C
MTTR defines how much data can be lost after a failure, while RTO defines how often failures occur.
- D
RPO measures the average repair time, so a 15-minute RPO means the system must be fixed within 15 minutes.
Show answer and explanation
Correct answer: A
Explanation
This question tests the practical distinction between disaster recovery objectives and equipment reliability metrics. In this scenario, the clinic's requirement to restore the scheduling system within 2 hours is the RTO, and the acceptable data loss of 15 minutes is the RPO. MTBF is often misunderstood as a recovery metric, but it only describes expected reliability over time and is commonly used for maintenance planning and hardware comparisons. MTTR describes average repair duration, which can influence whether an organization can meet its RTO, but it is not the same as the RTO itself. These definitions align with common disaster recovery and business continuity best practices used in IT operations and reflected in vendor and industry documentation on BC/DR planning: RPO addresses data loss tolerance, RTO addresses service restoration targets, MTTR addresses repair efficiency, and MTBF addresses failure frequency expectations.
- A. Correct.
Correct. MTBF (Mean Time Between Failures) is a reliability metric that estimates the average operational time between failures for repairable systems. It does not guarantee how fast an application or service can be restored. The clinic's requirement to restore service within 2 hours is the Recovery Time Objective (RTO). The requirement to lose no more than 15 minutes of data is the Recovery Point Objective (RPO). This option correctly separates reliability from recovery objectives.
- B. Incorrect.
Incorrect. This reverses the meanings of MTBF and RPO. MTBF is not about data loss tolerance; it is about expected time between failures. RPO is not hardware lifespan; it is the maximum acceptable amount of data loss measured in time, such as 15 minutes of transactions or updates.
- C. Incorrect.
Incorrect. MTTR (Mean Time To Repair) is the average time required to diagnose, repair, and restore a failed component or service, not the amount of data loss. RTO is not a measure of failure frequency; it is the target time to restore operations after an interruption. This option confuses repair, recovery, and reliability metrics.
- D. Incorrect.
Incorrect. RPO does not measure repair time. A 15-minute RPO means the organization can tolerate losing up to 15 minutes of data created since the last good backup, replication point, or recovery snapshot. The metric related to fixing or restoring systems is MTTR or, at the service level, RTO depending on the context.