Large MYSQL DB on single file
If you're concerned about the downtime mysqldump might cause you can look into hot backups. For example percona-xtrabackup.

Here is what I would do:


Create a slave with xtrabackup (set master_info_repository to
table if you have MySQL 5.6.2+)   
Have it replicated and let it catch up   
Stop the replication: stop slave 
(optional) Make a backup of master info file if you have MySQL older than 5.6.2
Make a note of the position with show slave status
Make the mysqldump
Destroy the database and all the files in mysql_datadir and remove all the relay logs
Restore the database with mysql_install_db and execute the dump (make sure you have file_per_table settings)
(only on &lt;5.6.2) If necessary restore replication (if it was in table than the dump contains the information so no need)


Then you can do the switchover and you'll have only a couple of seconds of downtime.