This article relates to Cisco TelePresence Video Communication Server Expressway.
Q. Why is VCS clustering better than the H.225 Alternate Gatekeeper mechanism?
A. VCS clustering is an active model where all VCSs in the cluster are always available for service. In the alternate gatekeeper model, the failover gatekeeper is essentially a hot-standby which can take up to 20 minutes to become active if the master gatekeeper fails.
VCS clusters can be distributed across datacenters therefore increasing service reliability.In the alternate gatekeeper model, both gatekeeper and alternate gatekeeper (2 box solution) need to be on the same subnet and therefore the same site.
VCS clusters allow you to load share by distributing the workload across different peers. It is very easy to add additional capacity by adding another VCS.