We have set up a portal using Yii Framework in Apache, PHP and MySQL. In the portal, there is a feature to export the data in dbf format, the extract takes around 7 minutes, but in those 7 minutes no other user can do anything in portal, not even login.
All tables are in MyISAM Engine.
I cannot provide you the link as its in our internal server.
Server is 4core Xeon Processor with 32 GB Ram.