Calibrating severity
The tension to hold
"Severe but plausible" is a constraint with two bounds.
Too weak: the scenario confirms the arrangements work, and the exercise becomes ceremony.
Too extreme: management refuses to draw conclusions — "that will never happen" — and the exercise is neutralised.
The useful zone sits beyond what the organisation has already lived through, but short of what it will consider fanciful.
The calibration method
Three references objectify the dial:
- The worst real incident the organisation has experienced. The scenario should exceed it by one notch.
- An incident at a peer in the same sector. It supplies plausibility: nobody can claim it does not happen.
- The combination of two events each of which has already happened separately. A supplier outage during a seasonal peak; unavailability while two key people are away.
The third reference is the most productive: it reaches high severity while remaining uncontestable, since each component has a precedent.
The six families to cover
A complete library covers the six mapping layers:
| Family | Typical scenario |
|---|---|
| Technology | Total, prolonged loss of a data centre |
| Data | Replicated logical corruption, restoration from backup required |
| Cyber | Ransomware with compromise of the administration directory |
| Third party | Abrupt failure of a critical provider with no notice |
| People | Simultaneous unavailability of 40% of a function's staff |
| Facilities | Main site inaccessible for an indeterminate period |
A programme that tests "data centre loss" three years running and never "provider failure" has a structural blind spot — all the more so as the second is now statistically more frequent.
The most frequent design error
Designing the scenario from the solution you want to validate. You then test the failover you know works, under the conditions you prepared for.
The scenario must be designed from the map, deliberately targeting the points identified as fragile. The objective is not to pass the exercise: it is to measure where the limit lies.
Key takeaways
- Severe means beyond what has already happened, not beyond the conceivable
- A scenario breaching no tolerance teaches nothing
- Plausibility is demonstrated by a sector precedent