rsync not updating files even with checksum flag

[Mark Osborne]

Hello everyone,

I am having a problem with rsync that I hope someone can help me figure 
out.  We are using rsync to sync up files between our staging and 
production ftp servers.  Basically internal users are allowed to upload 
files via a samba share to a staging server.  Those files are then synced 
out every 15 minutes via cron to our production ftp servers.

The problem occurs when a large file is being upload from a windows 
machine via the samba share.  If a rsync is instantiated during the time 
that the file is being uploaded the destination machines get the file with 
the correct filesize and timestamp.  Unfortunately, even though the file 
shows the correct size it is not a good copy of the file.  An md5sum of 
the files on both the source and destination machine returns different 
results.  I believe this occurs because windows automatically "reserves" 
the full size of the file and fills it out with 0s and then overwrites 
this as it goes along copying.  This wouldn't be a big deal except, 
subsequent runs of rsync (even with -c) fail to overwrite the file. 

I have tested running an rsync while I was copying the file over to the 
source directory locally (not via samba) and the file was corrupted. 
However after running an rsync again, the file was updated.  Basically the 
problem only occurs when uploading the file via the samba share. 

I know I could use the -I flag to ignore times and filesizes, but from my 
understanding this would result in resyncing every file every time, and 
this is not what we want.  We are currently using rsync 2.5.5 on the 
source machine, and 2.5.7 on the 2 destination machines, but I have also 
tested using 2.6.8 on both source and destination with the same results.

Has anyone else experienced this problem before, or have any ideas for a 
fix?  Let me know if I'm not being clear enough, or any other information 
I can provide.

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Mark Osborne
Web Systems Engineer
mark.osborne at ni.com
(512) 683-5019
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