The Sun Java System Directory Server topology includes four masters and four read-only replicas. Directory Server is the corporate directory server used to control access to Web-based applications. The directory server has a single root suffix, dc=gt,dc=com; information about the users are stored in the ou=people, dc=gt,dc=example,dc=com container with uid as the naming attribute.
Two masters and two read-only replicas are located in the United States (a separate configuration directory in the United States stores configuration information for these systems).
Two masters and two read-only replicas are located in Europe (a separate configuration directory in Europe stores configuration information for these systems).
All four masters have replication agreements with each other, but the four read-only replicas only have replication agreements with two of the masters as shown in the following figure.
Identity Synchronization for Windows treats hub replicas the same as read-only replicas. In many scenarios, using a hub replica is preferred to using a read-only replica because a hub can be easily promoted to a master.