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by ehzy 1415 days ago
The point is to not lose any data. In the example, if you need 4 drives to store 16 TB of data instead of 1, your probability of data loss is 18.6% vs 5%.
1 comments

How do you get 18.6%?
Prob of no failure in 1 drive is 95%. Prob of no failure in 4 drives is .95^4 = .816. Prob of failure in any of 4 drives is 1-.816 = 18.6%

Disclaimer: I got a D in Probability & Statistics