Cisco Systems Servers Manuale Utente

The frequency with which your Cisco Secure ACS servers replicate can have 
important implications for overall AAA performance. With shorter replication 
frequencies, a secondary server is more up-to-date with the primary server. This 
allows for a more current secondary Cisco Secure ACS server if the primary 
Cisco Secure ACS server fails, including a more current CiscoSecure user 
database.

There is a cost to having frequent replications. The greater the frequency of 
replication, the higher the load on a multi-server Cisco Secure ACS architecture 
and your network environment. Because Cisco Secure ACS transfers replicated 
data more often, network traffic load is much higher. Also, processing load on the 
synchronizing systems is increased. Replication consumes system resources, and 
the more often replication is repeated, the greater the impact on the 
Cisco Secure ACS server’s AAA performance.

This issue is more apparent with large databases or frequently changing 
databases. Database replication is a non-incremental, destructive backup. In other 
words, it completely replaces the database and configuration on the secondary 
Cisco Secure ACS server every time it is run. Therefore, if the database being 
transferred is large, the amount of data being transferred can be substantial, and 
the processing overhead can also be large.

Several important points bear consideration when implementing the CiscoSecure 
Database Replication feature:

Cisco Secure ACS only supports database replication to other 
Cisco Secure ACS servers. All Cisco Secure ACS servers participating in 
CiscoSecure database replication must run the same version and patch level 
of Cisco Secure ACS.

Only suitably configured, valid Cisco Secure ACS hosts can be secondary 
Cisco Secure ACS servers. To add a secondary Cisco Secure ACS server, 
configure the Cisco Secure ACS server in the AAA Servers table in the 
Network Configuration section. When a Cisco Secure ACS server is added to 
the AAA Servers table, it appears for selection as a secondary 
Cisco Secure ACS server in the AAA Servers list under Replication Partners 
on the CiscoSecure Database Replication page.