On Tue, Mar 10, 2009 at 12:05 AM, Carlos E. R.
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On Monday, 2009-03-09 at 23:26 -0400, Greg Freemyer wrote:
dd if=/dev/sda of=/dev/sdc bs=1G conv=noerror
Please note, never use noerror without also using sync.
Why? I'm curious. I can make a guess, but I'm not sure, it is not mentioned in the manual:
noerror continue after read errors
sync pad every input block with NULs to ibs-size; when used with block or unblock, pad with spaces rather than NULs
Do you mean, that without "sync", the output would just skip the remaining bytes of a block after an error, meaning the output would simply be "smaller", with pieces missing?
Because, as Sid did an 'xfs_repair' on the result, it means either there was no error, or that the gaps were filled :-?
Look at the output of a dd run. dd if=/dev/zero of=/dev/null count=100 100+0 records in 100+0 records out 51200 bytes (51 kB) copied, 0.000172439 s, 297 MB/s The first 100 says 100 blocks read without error. the first zero is 0 failed blocks failed to read. The second 100 is the blocks written without error, and the second 0 is the failed block writes. If you don't use sync and there are 2 errors I believe you get: 98+2 records in 98+0 records out. i.e The failed blocks are not replicated in the destination at all With sync, you get: 98+2 records in 100+0 records out. I'm not sure what the exact output block has in it but at least part of it is zero filled. I always use a 4k block size to align my userspace behavior with the kernels normal page size. Greg
- -- Cheers, Carlos E. R.
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-- Greg Freemyer Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer First 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe, e-mail: opensuse-factory+unsubscribe@opensuse.org For additional commands, e-mail: opensuse-factory+help@opensuse.org