Specifications

A single Open Directory master server can have up to 32 replicas and each of those
replicas can have up to 32 replicas, which gives you 1,056 replicas of a single Open
Directory master server.
This creates a two-tier hierarchy of replica servers. The rst tier of replicas, which
are the direct members of the Open Directory master, are called relays if they have
replicas, because they relay the data to the second tier of replicas.
Also, cascading replication does not require that a single Open Directory master server
maintain a transaction record of each replica server. The master server only keeps a
maximum of 32 replica transaction records, which improves performance.
The following illustration shows the two-tier hierarchy of the cascading replication model.
Replica ReplicaReplica ReplicaReplica ReplicaReplica Replica
Open Directory
Master
Relay
(Replica)
Relay
(Replica)
Relay
(Replica)
Relay
(Replica)
Planning the Upgrade of Multiple Open Directory Replicas
If your Open Directory master manages more than 32 replicas, your organization must
migrate to a cascading replication. The cascading replication model will improve your
Open Directory server performance.
When planning for your migration consider the locations of your replica servers and
your network topology to help determine how to reorganize your replicas into a
hierarchal structure.
For example, you would not want to have an Open Directory master on the West coast
replicating to a replica on the East coast.
Note: If your Open Directory master has fewer than 32 replicas, migration is not
necessary.
62 Chapter 4 Open Directory Planning and Management Tools