If you migrate a VM to another node via Proxmox it will rsync the server twice. But you never know how long the first one will take. So before I use the migrate function I use this little line to do a manual rsync.
This way I can rsync whenever I want and start the migrate on the end of the evening so the night will not take unexpected long 🙂
/usr/bin/rsync -aHAX --delete --numeric-ids --sparse /var/lib/vz/private/100 root@10.0.0.1:/var/lib/vz/private