The filesystem is already mounted with no atime.(but it is a vmware guest, with ide drive this still needs to be fixed)
I read the slapd-bdb man page and I get now that slapd's conf is complementing the DB_CONFIG file. But with setting this olcDbShmKey to 1 (removed it from DB_CONFIG). I am not seeing the slapd process constantly in iotop -o. Why is it not good to set this?
I also enabled dovecot auth caching and nscd