The shop that lost a day
An online shop's server fails at noon. The last backup was taken at midnight. It takes four hours to get the shop running again.
The owner asks two questions. How much work did we lose? How long were we down?
Five measures answer questions like these. You will use all five.
By the end of this lesson
Note
I can say what RTO, RPO, MTBF, MTTD and MTTR measure and work each one out.
Key words
| Word | What it means |
|---|---|
| RTO | recovery time objective: how long recovery may take after a disaster |
| RPO | recovery point objective: how much data you can afford to lose |
| MTBF | mean time between failures: how long a system usually runs before it fails |
| MTTD | mean time to detect: how long it takes to notice a problem |
| MTTR | mean time to recovery: how long a repair takes |
| Mean | the average: add the values, then divide by how many there are |
| Backup | a copy of data kept so it can be restored |
The cells students fill in are left blank in this preview.
Starter
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
RTO and RPO are targets
An organisation chooses two targets before a disaster.
The RTO is the longest time the systems may be down. The RPO is the most data you can lose, counted in time since the last backup.
In the hook, the RTO could be two hours. The RPO could be one hour. The shop missed both.
Worked example: did the shop meet its targets?
| Measure | Target | What happened | Met? |
|---|---|---|---|
| RTO | 2 hours down at most | 4 hours down | No |
| RPO | 1 hour of data lost at most | 12 hours lost, from midnight to noon | No |
The cells students fill in are left blank in this preview.
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.