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Network Redundancy Calculator

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

About Network Redundancy Calculator

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

Worked example

With the default values below, Network Redundancy Calculator returns System Availability of 99.999999%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Components installedaccepts 1–100 units
4 units
Components required to carry loadaccepts 1–100 units
3 units
Mean time between failuresaccepts 100–10,000,000 hours
50,000 hours
Mean time to repairaccepts 0.1–720 hours
4 hours

Results

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

Step by step

  1. 1Values used
  2. 2Network Redundancy
  3. 3System Availability= 99.999999
  4. 4Availability of One Component= 99.99200
  5. 5Expected Downtime= 0.003 minutes/year
  6. 6Spare Units= 1 units
  7. 7Order of Availability= 8.19 nines

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

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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