Disc burning "verify" alternative

[ramalam]

I'm backing up to BD-R's now but the verify option (Toast) is a real killer - it effectively doubles the time it takes.

Here's my alternative, tell me if there's a problem with it: After the burn select all original files and "Get Summary Info", do the same with the burned files, then simply compare the sizes byte for byte. Isn't this a faster method of verifying? If there's an error in the burn then at least one byte should be off, correct?

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[stiligFox]

It sounds good in theory, but I think the idea behind verifying the disc to make sure each byte is the right one -- it might copy the correct number of bytes, but some of them might be jumbled, or wrong altogether. (My guess)

 

[chown33]

If there's an error in the burn then at least one byte should be off, correct?

Incorrect. You're saying there can't be two files with different contents, which have the same size. This is easily shown to be false. Simple consider one file with the word "wrong", and another file with the word "right". Length of each file is 5 bytes. But they clearly contain different data.

The only way to confirm a burn really worked is by reading every byte on the burned disc and comparing with every byte of the original data. There is no substitute for reading from the just-burned disc.

We could get into the error characteristics of optical discs, or the error-correcting capabilities, but it's enough to know that comparing bytes is necessary for 100% confirmation of data.