According to mysql.com, running two different versions is possible. http://dev.mysql.com/doc/refman/4.1/en/multiple-unix-servers.html http://dev.mysql.com/doc/refman/5.5/en/multiple-unix-servers.html http://dev.mysql.com/doc/refman/5.6/en/multiple-unix-servers.html I'm asking about this because I'm running an old version of mysql and don't want to upgrade in case the existing php scripts and mysql statements fail after upgrading. If it were possible to set up another mysql 5 server seperate as outlined in the links above, then I could create test directories of the same existing php scripts, point them to the mysql 5 server and test, while retaining the existing mysql 4 setup for the production websites. Has KH experience in setting up additional mysql servers on clients VPS's before? (not sure which mysql version cpanel/whm is currently up to).