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This setup is similar to the previous one with the exception that both LDAP servers are masters. It is possible to have several servers acting as masters for directory information, with each master responsible for updating other master servers and replica servers. This is referred to as peer replication. Some vendors also refer to this replication topology as multi-master. See Figure 15-17.
Peer replication can improve performance, availability, and reliability. Performance is improved by providing a local server to handle updates in a widely distributed network. Availability and reliability are improved by providing a backup master server ready to take over immediately if the primary master fails. Peer master servers replicate all client updates to the replicas and to the other peer masters, but do not replicate updates received from other master servers.
Figure 15-17 LDAP and Load Balancer, multi-master/peer replication
If a high volume of directory changes could occur in a brief interval of time, then you should consider using an "always true" Load Balancer rule and adding just one LDAP server to that rule to ensure that all requests get directed to only one LDAP server while still ensuring that the other LDAP server can service requests in the event of a failure of the designated LDAP server associated with the always true rule.
