rsync - Jun 2006 - DO NOT REPLY [Bug 3846] New: rsync silently transfers blocks of zero bytes on read errors

https://bugzilla.samba.org/show_bug.cgi?id=3846

           Summary: rsync silently transfers blocks of zero bytes on read
                    errors
           Product: rsync
           Version: 2.6.8
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: major
          Priority: P3
         Component: core
        AssignedTo: wayned@samba.org
        ReportedBy: jochen@penguin-breeder.org
         QAContact: rsync-qa@samba.org


when rsync fails to read part of a file, it silently transfers blocks of zero
bytes instead of the actual data.

This renders rsync useless for most kinds of backup applications, because in
case of a hardware failure, all backups may be already destroyed by blocks of
zeros, and you have a hard time to figure out which files are intact (i.e.
should contain such blocks) and which are not (i.e. rsync introduced such
blocks), because there isn't even a information in any log.

I'd suggest to introduce an option --ignore-read-errors which exhibits the
current behaviour and fail on read-errors as per default.


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------- Comment #1 from hashproduct+rsync@gmail.com  2006-06-18 19:11 MST
-------
Rsync sends zeroes in an attempt to get as much of the new data to the receiver
as possible; one could argue that the receiving rsync should take the data from
the same offset in the basis file instead.  It also sabotages the post-transfer
MD4 checksum on lines 355-357 of match.c:

        /* If we had a read error, send a bad checksum. */
        if (buf && buf->status != 0)
                file_sum[0]++;

That will cause the receiving rsync to delete the temporary file on line 641 of
receiver.c, leaving the old but valid version of the source file intact.  Rsync
will produce a message like this:

   WARNING: <file> failed verification -- update discarded (will try
again)

So I don't think there's a problem.  Wayne, please correct me if I am
wrong.


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------- Comment #2 from jochen@penguin-breeder.org  2006-06-21 08:42 MST -------
ah, sorry. After double-checking this only happened with 2.6.5, i.e. the
current version 2.6.8 actual throws an error message.


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wayned@samba.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
            Version|2.6.8                       |2.6.5




------- Comment #3 from wayned@samba.org  2006-09-17 17:53 MST -------
Fixed in newer versions.


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