saving space
Use the "dateext" option when using logrotate
This prevents the old log files changing name every time the logfiles are rotated (i.e. log.1.gz becomes log.2.gz etc.); when a filename changes, even though the contents are the same, then dirvish / rsync won't be able to hardlink the different names, causing data duplication.
The "dateext" option tells logrotate to use a !YYYYMMDDhhmmss extension, which has the additional bonus of sorting chronologically which .9, .10, etc don't.
Check that your version of logrotate supports dateext!