Network Redundancy Calculator

Derive component availability from MTBF and MTTR, then the availability an N+M redundant group delivers.

Inputs

Components installedunits

Components required to carry loadunits

Mean time between failureshours

Mean time to repairhours

System Availability

99.999999%

Availability of One Component

99.99200%

Expected Downtime

0.003minutes/year

Spare Units

1units

Order of Availability

8.19 nines

Step by step

Values used
Components installed = 4 units; Components required to carry load = 3 units; Mean time between failures = 50,000 hours; Mean time to repair = 4 hours
Network Redundancy
component availability = MTBF ÷ (MTBF + MTTR); system unavailability = (1 − availability)^(spares + 1), where spares = installed − required.
System Availability
= 99.999999
Availability of One Component
= 99.99200
Expected Downtime
= 0.003 minutes/year
Spare Units
= 1 units
Order of Availability
= 8.19 nines

How it works

A single component's availability follows directly from how often it fails and how long repairs take. Adding spares multiplies the failure probabilities together, so each additional redundant unit removes roughly one more order of magnitude of downtime — provided failures really are independent. It converts an SLA target into a concrete answer about whether N+1 is enough or N+2 is required, and it exposes MTTR as usually the cheapest lever to pull.

Formula

Network Redundancy

component availability = MTBF ÷ (MTBF + MTTR); system unavailability = (1 − availability)^(spares + 1), where spares = installed − required.

MTBF: Mean operating hours between failures of one component
MTTR: Mean hours to detect, dispatch and repair
spares: Installed units beyond the number needed to carry load

Frequently Asked Questions

How is Network Redundancy calculated?

component availability = MTBF ÷ (MTBF + MTTR); system unavailability = (1 − availability)^(spares + 1), where spares = installed − required. A single component's availability follows directly from how often it fails and how long repairs take. Adding spares multiplies the failure probabilities together, so each additional redundant unit removes roughly one more order of magnitude of downtime — provided failures really are independent.

Why does Network Redundancy matter?

It converts an SLA target into a concrete answer about whether N+1 is enough or N+2 is required, and it exposes MTTR as usually the cheapest lever to pull.

What values do I need to enter?

This calculator takes 4 inputs: Components installed, Components required to carry load, Mean time between failures, Mean time to repair. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

Why does MTTR matter more than MTBF?

Availability depends on the ratio of repair time to uptime, and MTTR is the term you control. Halving MTTR from four hours to two doubles availability just as effectively as doubling MTBF, and it costs a spares cupboard rather than new hardware.

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