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Science / DevOps / Grade 9 / sd9r1

Recovery Goals: Compare Three Backups

Compare data gaps and complete recovery times without confusing one goal with the other.

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Practice comparing recovery goals

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The recovery point objective (RPO) limits the time gap between the recovered data point and the outage. The recovery time objective (RTO) limits the whole interruption until service is working again. Compare each measured interval with its own maximum. Meeting one limit does not meet both. A rehearsal is evidence, not a promise about every future outage.

Worked example

An outage is at 09:20. A copy covers data through 09:12, so the data gap is 8 minutes. Detection takes 1 minute, restoration 3 and checking 2, so service returns after 6 minutes. Limits of 10 minutes for the data gap and 6 for interruption are both met, including the exact time limit.

Outage 14:30. Data gap limit 15 minutes; interruption limit 8 minutes. Rows list copy A: data through 14:05, detection 2, restore 1, checks 3; B: 14:26, 1, 2, 7; C: 14:15, 2, 3, 3. All durations are minutes.
Subtract for the data gap. Add every stage for the interruption.

Three separate paper rehearsals

The outage is at 14:30. The maximum data gap is 15 minutes and the maximum interruption is 8 minutes. A covers data through 14:05: detection 2, restore 1, checks 3 minutes. B covers through 14:26: detection 1, restore 2, checks 7 minutes. C covers through 14:15: detection 2, restore 3, checks 3 minutes. Each copy passes its own content checks. Stages are sequential, include all delays, and service returns only after checks finish. Each row is a separate rehearsal, not time added to another row. No real records are changed.

Question 1 What is the data gap for copy A, in minutes?
Question 2 How long is the complete interruption in rehearsal B, in minutes?
Question 3 Which rehearsal meets both stated limits?
Question 4 Does C need to be strictly below both limits to meet them?
Question 5 Two other copies have the same row count. Does that alone prove they have the same data gap?