Specifications

Chapter 4 Open Directory Planning and Management Tools 61
Replica version Mac OS X Server v10.5 or later
master
Mac OS X Server v10.4 master
Mac OS X Server v10.5 or later
replica
Yes No
Mac OS X Server v10.4 replica No Yes
Replica Sets
A replica set is an automatic conguration that requires each service that Open
Directory manages (LDAP, Password Server, and Kerberos) to look for and use the same
replica server. This helps ensure that client computers choose the same replica server
when using Open Directory services and helps prevent slow login.
Cascading Replication
Mac OS X v10.4 used a hub-spoke model for replicating Open Directory master servers.
This required each Open Directory master to maintain a transaction record for each
replica server.
The following illustration shows the hub-spoke model used in Mac OS X v10.4.
Replica
Replica
Replica
Replica
Replica Replica
Open Directory
Master
In addition, there was no predened limit to how many replica servers an Open
Directory master could manage.
If an Open Directory master had 1,000 replicas to manage, it could have performance
issues if replicas continued to be added. This is similar to having one manager for 1,000
employees, which is an unmanageable situation.
Mac OS X Server v10.5 and later use cascading replication to improve scalability and
resolve performance issues with the older hub-spoke model of replication. The use of
cascading replication helps limit the number of replica servers that can be supported
by a single Open Directory master server.