Red Hat ENTERPRISE LINUX AS 2.1 Installation Manual page 111

Section 6.6:LVS Cluster — A Block Diagram 111
Figure 6–4 Components of a Running LVS Cluster
The pulse daemon is runs on both the active and passive LVS routers. On the backup router, pulse
sends a heartbeat to the public interface of the active router to make sure the active router is still
functioning correctly. On the active router, pulse starts the lvs daemon and responds to heartbeat
queries from the backup LVS router.
Once started, the lvs daemon calls the ipvsadm service to configure and maintain the IPVS routing
table in the kernel and starts a nanny process for each configured virtual server on each real server.
Each nanny process checks the state of one configured service on one real server, and tells the lvs
daemon if the service on that real server is malfunctioning. If a malfunction is detected, the lvs
daemon instructs ipvsadm to remove that real server from the kernel's IPVS routing table.