raid6 /

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Probability of a RAID 6 (double parity) failure, leading to total loss of all data.

Array/shelf configuration:

Drives:         23 (2 parity drives)
Total capacity: 12TB
MTTR:           16 hours (rebuild time)
Hot spares:     infinite

Drive parameters:

Capacity:       585GB
MTBF:           43800 hours
URE rate:       1e+16

Annual probability that 3 drives fail within the MTTR window (thereby destroying all data):


Annual probability that 2 drives fail (3.851%), combined with an Unrecoverable Read Error (URE) during the rebuild (0.011%):