If you ran 'cmp' on them - check your $HISTFILE, maybe you can get (at least a few) of the filenames from there.
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Question
rsync corrupts files
I've used rsync to copy around 300GB of data in the form of small text files, large binary executables/videos, word documents etc. Source and target are both on different md raid1 devices on the same machine. The rsync command was:
# rsync -aHxv /mnt/src/ /mnt/dst/
All seemed to work well, but then I did a quick
# diff -r /mnt/src /mnt/dst
Which showed some files that differed. Around 8-10 files, a far as I can remember. A cmp -l on such a file would always return a single byte difference, and it was always the value in the old file incremented by one:
# cmp -l /mnt/src/file.exe /mnt/dst/file.exe
82778 24 25
This seems to be quite systematic. I still have the source files, so now I did a
# rsync -caHxv /mnt/src/ /mnt/dst/
and this effectively re-transfers all the corrupted files, this time without corruption.
Rsync is supposed to check the checksum of transfered files, so how is this corruption even possible?
Is there something I have to take care of when transferring large volumes of data locally with rsync? How can I be sure that this doesn't happen again (without using -c, because this takes ages)?
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Answers
The corrupted files were not hardlinked, no.
rsync without the -c option didn't find anything new, I ran it multiple times. That's because it only looks at some attributes like the modification timestamp and doesn't do a full checksum at every run.
The corrupted files were rather large binary files, but I didn't see any pattern in them.
Do you remember if this off-by-one byte was at the end of the file? How big is /mnt/dst/file.exe? Again, is it an actual (Windows?) executable file or just a file of binary data?
It is just so *odd* that only one byte would be off and that the byte offset would also be only 1 in a handful of files over so many megabytes (or gigabytes).
Ok, it seems the problem is not with rsync... After having a diff give me a difference in a binary file, and a second diff run didn't I let the following command run for a while:
# while true; do diff /mnt/src/somefile /mnt/dst/somefile; done
Where somefile is a file in which a difference was reported earlier, size 372 MB.
It ran for a couple of minutes without returning anything, then suddenly it started printing "Binaryfiles /mnt/src/somefile and /mnt/dst/somefile differ" for about 2 minutes (and during that time cmp -l returned: 215286618 250 251. So again a one byte difference). Then it stopped again, and cmp -l reported no difference again.
I'd say it's a hardware problem... Just not sure which part is the culprit. My guess would be the mainboard.
I wonder if you could reproduce it.
Copy just a subset of files (like a directory containing a file that didn't copy correctly before) to a new, empty directory (and don't use the '-c' flag for rsync) and see if the same corruption occurs.
If you can reproduce it, I'd file a bug with on the rsync site.
If I were you, I would have selected http:#25361130 and assigned no points, but I guess closing works, too.
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by: nemws1Posted on 2009-09-17 at 12:27:47ID: 25359965
Hmm.. you have -H defined to preserve hard links. Depending on the how the files were copied, if 'rsync' found the original first or the hard-link first, that would account for the very-minor difference (I think).
It would be really nice to know exactly which files where bad and if they had any hard links going to them.
Does this (with the -n)
rsync -aHxv /mnt/src/ /mnt/dst/
Report any new differences? Do don't by any chance have a list of the "bad" files?