On a Debian6 / ISPConfig3 VPS I would like to upgrade from MySQL 5.1 to 5.5. Are there any contraindications regarding ISPConfig3? It is expected that ISPConfig will automatically upgrade MySQL? If not, is there a document that explains how to upgrade without doing damage? Thanks.
ISPConfig works fine with mysql 5.5, so I dont expect any ispconfig related problems when you update your mysql server.
To migrate from Mysql to Mariadb use http://beginlinux.com/server/server-management/mysql-maria-database-migration-tutorial Please take proper backups before proceeding.