REDUNDANT SYSTEM COMPONENTS

r1

r2

R = ?

BOTH COMPONENTS MUST FAIL

FOR SYSTEM TO FAIL.

PROBABILITY OF SYSTEM FAILURE: P = 1 - R

p1 = 1 - r1 and p2 = 1 - r2

P = p1 * p2 = (1 - r1) * (1 - r2)

= 1 - r1 - r2 + r1 * r2

R = 1 - P = r1 + r2 - r1 * r2

EXAMPLE :

r1 = r2 = 0.8

R = 0.8 + 0.8 - (0.8 * 0.8)

= 1.6 - 0.64

= 0.96

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