Research — Illustrative (draft, unvalidated)

K-of-N availability

Pick N components, slide how many of them K must be available, and set each one's availability. The system availability is computed exactly, without assuming the components are identical. The independence assumption behind it is printed under every result.

Units, required slots and nines gauge (fixed illustrative drawing)

What-if: mark a unit failed (shows whether K survive; not a probability)

Topology preset · N = components needed

Components N

Required available K

Component availability

Same availability for all (untick to set each one)

Component 1

Component 2

Component 3

Component 4

Component 5

Component 6

System availability status

System availability

Topology

Expected downtime (derived)

How the check read it

Client-side port:the logic and table in this page are a TypeScript port of the harness function, checked against values exported from the Python tests. Not a live API call. Domain maturity, quoted from the research page: “Draft; no reliability or controls engineer has reviewed it yet. The availability math is cross-checked against closed-form series, parallel and 2-of-3 cases, and an AI-assisted pre-review found and fixed three issues. IEEE 493 and ISA-75.19.01 were not read directly.” Only the system availability comes from the harness function; the nines figure and the downtime per year are plain arithmetic done in this page from that availability (assuming a 365-day, 8760 h year) and are labeled as derived. The 2N preset follows the function’s docstring: two pre-aggregated sides, one required.Real function this maps to:calculate_redundant_system_availability.Not modeled: common-cause failures (shared feeds, shared cooling loops, shared fire zones), which make this result optimistic; repair times and failover timing; component reliability data (availabilities here are values you choose, not catalog figures); and Uptime Institute tier mapping, which the function leaves to the caller. The unit drawing and the failed/working what-if toggles are illustrative: they show how many units must be up, not a probability.See also:K-of-N availability, auto walk · Failover race