there is a check next to logger in the admin UI and when I use zmcontrol start it is always among the services listed. Plus there are two process attributed to it:
/opt/zimbra/logger/mysql/bin/mysqld --defaults-file=/opt/zimbra/conf/my.logger.c ...
/bin/sh /opt/zimbra/logger/mysql/bin/mysqld_safe --defaults-file=/opt/zimbra/con ... |