Red Hat CLUSTER SUITE - FOR RHEL 4 Overview page 33

Chapter 1. Red Hat Cluster Suite Overview
To balance the load across the real servers.
•
To check the integrity of the services on each real server.
•
The backup LVS router monitors the active LVS router and takes over from it in case the
active LVS router fails.
Figure 1-19 provides an overview of the LVS components and their interrelationship.
Figure 1-19. Components of a Running LVS Cluster
The daemon runs on both the active and passive LVS routers. On the backup LVS
pulse
sends a heartbeat to the public interface of the active router to make sure the
router,
pulse
active LVS router is properly functioning. On the active LVS router,
daemon and responds to heartbeat queries from the backup LVS router.
Once started, the
lvs
IPVS (IP Virtual Server) routing table in the kernel and starts a
configured virtual server on each real server. Each
configured service on one real server, and tells the
server is malfunctioning. If a malfunction is detected, the
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
addresses (MAC address) of the backup LVS router, sends a command to the active LVS
daemon calls the
to reassign all virtual IP addresses to the NIC hardware
send_arp
utility to configure and maintain the
ipvsadm
process checks the state of one
nanny
daemon if the service on that real
lvs
lvs
starts the
pulse
process for each
nanny
daemon instructs
ipvsadm
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lvs