your instructions to upgrade ee stack (pre 2.2) mysql to percona worked, but some notes:
apt-get purge mysql-server*did not work, i had to to remove the "*"and tab complete instead (otherwise i get
no matches found: mysql-server*)
In the last step, import database, one pv command is not recognized:
command not found: pv(in fact this last step does not seem necessary as without it my db was back up) you might want to edit this.