To synchronize 2 volumes with rsync and also delete the files from the destination backup or second volume which do not exist on the source master or first volume, use the following rsync command:

rsync -avh <source master volume>  <destination backup volume>  --delete --ignore-errors

for example:

rsync -avh /media/kevin/GEMINI/DATAVOLUME/ /media/kevin/DATAVOLUMELUKS/ --delete --ignore-errors

Its important to include the

--ignore-errors

directive, else the deletion will fail!