Alfresco stores the file content in the file system and indexes them from a Database. The alf_data directory is where all contents reside and that will be by default under the root of the Alfresco installation and the property file could be found under tomcat\shared\classes\alfresco-global.properties folder. Other proprietary ECM's store the content in the Database, in that case the DB size keeps growing, which is most likely to cause implications on performance.
