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RAID Rebuild Risk Calculator

Quantify the vulnerable rebuild window from a drive data sheet and observed speed, then check the conditions that should stop the work before it starts.

Model scope

Time assumes the full replacement drive is written at the entered speed and efficiency. Read exposure assumes all surviving parity drives are read; RAID 10 reads the affected mirror mate.

Reading the probabilities

URE uses the data-sheet bit error rate as independent trials. AFR is prorated to the rebuild window. These are statistical exposure estimates, not guarantees or predictions of data loss.

Stop condition: Do not begin without a verified independent backup, or when SMART warnings, bad sectors, or abnormal temperatures are present. Verify the vendor procedure and RAID 10 mirror placement first.