Currently Being ModeratedMar 18, 2012 6:01 PM (in response to grnfrog55)
--log-file will create the log file (assuming you have permission to create the file in the specified directory).
Have you tried it and it didn't work? If so, did you get any error messages?
NOTE: The most up to date rsync is included as part of Carbon Copy Cloner, and the up executable can be found at Carbon Copy Cloner.app/Contents/MacOS/ccc_helper.app/Contents/MacOS/rsync