sudo -sThat takes care of the backup and transfer, so all that is needed is a quick mapping of IP addresses on the new host and a restore. Disable the client on the initial server to ensure that mail doesn't get delivered and lost.
echo 'client_name' | /opt/psa/bin/pleskbackup --clients backup_file -list -
scp backup_file_name username@remote_host:
ssh username@remote_hostYou'll need to ensure that the mapping of the domains for the client is done correctly if there are multiple IP addresses on both systems. Most of the time, Plesk gets it correct.
/opt/psa/bin/pleskrestore --create-map backup_file -map map_name
/opt/psa/bin/pleskrestore --restore backup_file -level clients -map map_name
Flick the DNS and all is done with minimal downtime.