Typically, overhead of VCS kernel components is minimal. Kernel components provide heartbeat and atomic information exchange among cluster systems. By default, each system in the cluster sends two small heartbeat packets per second to other systems in the cluster.

Heartbeat packets are sent over all network links configured in the /etc/llttab configuration file.

System-to-system communication is load-balanced across all private network links. If a link fails, VCS continues to use all remaining links. Typically, network links are private and do not increase traffic on the public network or LAN. You can configure a public network (LAN) link as low-priority, which by default generates a small (approximately 64-byte) unicast packet per second from each system, and which will carry data only when all private network links have failed.