benefit of using the 1:1 redundancy scheme is that it enables you to balance
the devices over the primary and backup subscriber pairs.
With load balancing,
you can move up to half of the device load from the primary to the secondary
subscriber by using the Unified Communications Manager redundancy groups and
device pool settings. In this way, you can reduce by half the impact of any
subscriber becoming unavailable.
To plan for 50/50
load balancing, calculate the capacity of a cluster without load balancing and
then distribute the load across the primary and backup subscribers based on
devices and call volume. To allow for failure of the primary or the backup, the
total load on the primary and secondary subscribers must not exceed that of a
single subscriber. In a 1:1 redundancy pair, you can split the load between the
two subscribers, configuring each subscriber with half of the agents. To
provide for system fault tolerance, make sure that all capacity limits are
observed so that Unified CCE agent phones, Unified IP phones, CTI limits, and
so on, for the subscriber pair do not exceed the limits allowed for a
devices and call volumes as equally as possible across all active subscribers.
For instance, distributing the Unified CCE agents, CTI ports, gateways, trunks,
voicemail ports, and other users and devices among all subscribers equally,
minimizes the impact of any outage.
information about general call processing topics such as secondary TFTP servers
and gatekeeper considerations, see the
Cisco Collaboration System
Solution Reference Network Designs at