OpenLDAP can be used as a persistent entry cache for Penrose.
database bdb suffix "dc=Example,dc=com" rootdn "cn=Manager,dc=Example,dc=com" rootpw secret updatedn "cn=Replicator,ou=Users,dc=Example,dc=com" updateref "ldap://localhost:10389" directory /usr/local/openldap/var/openldap-data index objectClass eq access to * by * auth by dn.base="cn=Replicator,ou=Users,dc=Example,dc=com" write