ITPEC FE Morning April 2022 Question 16
ITPEC FE Morning April 2022 — Question 16 of 80
Parallel system availability — compare configurations to find the highest uptime.
Formula: parallel availability = 1 - (1 - A)^n for n identical systems.
Calculate each option:
- •(a) Single system at 99%: availability =
0.99 - •(b) 4 systems at 70%:
1 - (0.3)^4 = 1 - 0.0081 = 0.9919 - •(c) 3 systems at 80%:
1 - (0.2)^3 = 1 - 0.008 = 0.992 - •(d) 2 systems at 90%:
1 - (0.1)^2 = 1 - 0.01 = 0.99
Ranking: 0.992 > 0.9919 > 0.99 = 0.99 → (c) wins.
Why not others:
- (a) 99% seems high, but parallel redundancy in (c) beats it
- (b) 99.19% is close but slightly below (c)'s 99.2%
- (d) Only 99% — same as a single 99% system
Key rule: Parallel availability = 1 - (1 - A)^n. More low-availability units in parallel can outperform a single high-availability unit.
AI-generated — may contain errors
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