[ryao]

3TB is 310^12 bytes assuming the decimal bytes used in the storage industry. The uncorrectable bit error rate is for the raw block storage. It does not include the low level formatting, which is no more than 20% of the storage on 512-byte sector drives and less than 10% on advanced format drives. The probability of an uncorrectable bit error when copying 3TB using decimal bytes) is approximately 1.5% under the assumption of a 5 in 10^15 uncorrectable bit error rate:

[1 - (1 - 5 10^-15)^(3 * 10^12)] ~ 0.01488...

If your 20% figure is accurate, the actual uncorrectable bit error rate would need to be something like 7 in 10^14. I am not disputing your empirical information, but your numbers are do not agree with it. The difference in what your numbers say and what you say is only about 1 order of magnitude. Doing statistical calculations with better records could allow the cause of that to be identified.

[ChuckMcM]

And to be clear, it is a bit error rate not a byte error rate. Nominal coding of data in magnetic media is 10 bits per 8 bit byte although a specific drive may use a different encoding on the platter. The Barracuda included 5120 NRZ encoded bits per sector and a 48 bit NRZ encoded checkword giving it a nominal 10.094 bits per byte. You're off by one decimal order of magnitude in the number of bits.

[ryao]

Just to be clear, I meant 3 * 10^12, not 310^12. The arithmetic that I posted uses the correct number.

[lutusp]

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