Install MariaDB and MySQL in CentOS 6 32bit in same server
MariaDB is a total drop-in replacement for MySQL - it even uses the same configuration files and folders.

If you're utterly sold on using both simultaneously, then you'd probably be best compiling from source and configuring all the folders manually. I am speaking from Debian derivative basis, so I may be off the mark regarding yum, but generally the package manager versions tend to be a simple replacement.

I would still run the following before taking the plunge, just in case something goes wrong:
mysqldump -u root -p --all-databases > alldbs.sql. Then you can easily restore with mysql -u root -p &lt; alldbs.sql.

Source: I recently attempted to do this myself, and found that there was no feature I used in MySQL that wasn't totally compatible with MariaDB.