Installation guide

Figure 1.19. Components of a Running LVS Cluster

The pulse daemon runs on both the active and passive LVS routers. On the backup LVS

router, pulse sends a heartbeat to the public interface of the active router to make sure the

active LVS router is properly functioning. On the active LVS router, pulse starts the lvs

daemon and responds to heartbeat queries from the backup LVS router.

Once started, the lvs daemon calls the ipvsadm utility to configure and maintain the IPVS (IP

Virtual Server) 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

IPVS routing table.

If the backup LVS router does not receive a response from the active LVS router, it initiates

failover by calling send_arp to reassign all virtual IP addresses to the NIC hardware addresses

(MAC address) of the backup LVS router, sends a command to the active LVS router via both

the public and private network interfaces to shut down the lvs daemon on the active LVS

router, and starts the lvs daemon on the backup LVS router to accept requests for the

configured virtual servers.

Linux Virtual Server