I have a quick question about storage of authentication plugin settings: Where do they go? If for example I save the hostname test.hostname.local into the CAS server configuration page at "server/admin/auth_config.php?auth=cas" and then check for its value in the moodle database within the table: mdl_config_plugins, I see that the value has been updated. But, if I change this value directly in the database, it is NOT reflected in the site administration page. This almost suggests that this setting is saved in two places.
you are probably using a Moodle version that includes the MUC (Moodle Universal Cache). This component caches a great deal of information to speed up many operations (including access to the DB). So it may happen that as you are not doing any changes to the setting through the Moodle code, the MUC still holds the (previous) cached, value as it assumes it's still "fresh" (valid). And when the config screen asks for the setting value from the DB, the MUC returns that value.
You can purge (invalidate) the caches by going to Administration >> Site Administration >> Development >> Purge all caches