Verify after copy

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Thany
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Post by *Thany » 2014-03-10, 13:30 UTC

HolgerK wrote:Did you miss TC 8.50?

Copy dialog -> [_] Verify (directly above the "Options" button)
I did not miss 8.5. Just didn't install it yet, and didn't realize this was a new thing. Excellent work, ghisler :)
sky66 wrote:Configuration => Options... => Copy/Delete => [_] Verify after copying (MD5 checksum)
I think it's been said: verifying by checksums is not a true verification. It's just checking if data matches the checksum. But it doesn't feel right to me to generate a 128-bits checksum for a 6GB file...

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Horst.Epp
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Post by *Horst.Epp » 2014-03-10, 15:23 UTC

Thany wrote:
HolgerK wrote:Did you miss TC 8.50?

Copy dialog -> [_] Verify (directly above the "Options" button)
I did not miss 8.5. Just didn't install it yet, and didn't realize this was a new thing. Excellent work, ghisler :)
sky66 wrote:Configuration => Options... => Copy/Delete => [_] Verify after copying (MD5 checksum)
I think it's been said: verifying by checksums is not a true verification. It's just checking if data matches the checksum. But it doesn't feel right to me to generate a 128-bits checksum for a 6GB file...
Sorry but you are kidding :D
The probabiliity for a wrong checksum together with an write error is small enough to live with it.
There is absölutely no need to make more than a checksum comparison.

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byblo
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Post by *byblo » 2014-03-10, 16:41 UTC

Thany wrote:I think it's been said: verifying by checksums is not a true verification. It's just checking if data matches the checksum. But it doesn't feel right to me to generate a 128-bits checksum for a 6GB file...
I thought the same. Isnt crc32 faster and enough for this feature?

avinatbezeq
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Re: Verify after copy

Post by *avinatbezeq » 2019-08-07, 07:02 UTC

Old Old thread. I know. I'm just trying to save my data from an ailing SSD, copying it to the NAS, and I saw the option in the dialog, googled it and reached here.

Good thing, thought. Now , to avoid the cache issue, I'll restart both computer and NAS before I use Synchronize Dirs to verify the copy :)

It's really out of curiosity: As the CRC is calculated on the source computer this means that the copied info has to be read from the destination compute and sent back to the source computer for CRC calculation. So, a CRC comparison should be SLOWER than a bit-by-bit one! Assume there is an error on the first bit. As it's detected immediately, the "mismatch error" could be given immediately, not after the whole data is re-read and sent back over the network...

:)

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