ionice -c scheduling_class -n priority_nice_value command
scheduling_class 0 for none, 1 for real-time, 2 for best-exertion, 3 for inactive
priority_nice_value 0-7 are legitimate information (need levels)
ionice -c 3 rsync rsync --delete -avz /srv/ /mnt/backup
rsync --delete -avz -e ssh -p 10022 des@remoto:/srv /srv/datos/backup/