Because database replication in a Cisco Secure ACS is a "top down" approach, using the cascade method minimizes replication-induced downtime on the master server. If the master server is not used for authentication services, but for database maintenance only, the cascade method may not be as critical. However, when traveling across time zones, particularly international time zones, it may be necessary to consider using the cascade method going to remote secondaries. In this case, consider using At specific times versus Automatically triggered cascade (see Figure 5). This will allow "local" replication to take place during a time that will minimize the impact on user authentication. During these long distance replications, replicating to the backup or secondary server first also helps reduce this impact. Figure 6 shows a hypothetical deployment for replication where each region has both a primary and a secondary Cisco Secure ACS deployed. In the scenario, replication is made to the secondary servers to avoid replication downtime to the primary.
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