Linux Virtual Server Overview; A Basic Lvs Configuration - Red Hat CLUSTER SUITE - CONFIGURING AND MANAGING A CLUSTER 2006 Manual

Linux Virtual Server Overview

Red Hat Enterprise Linux LVS clustering uses a Linux machine called the active router
to send requests from the Internet to a pool of servers. To accomplish this, LVS clusters
consist of two basic machine classifications — the LVS routers (one active and one backup)
and a pool of real servers which provide the critical services.
The active router serves two roles in the cluster:
To balance the load on the real servers.
•
To check the integrity of the services on each of the real servers.
•
The backup router's job is to monitor the active router and assume its role in the event of
failure.
7.1. A Basic LVS Configuration
Figure 7-1 shows a simple LVS cluster consisting of two layers. On the first layer are
two LVS routers — one active and one backup. Each of the LVS routers has two network
interfaces, one interface on the Internet and one on the private network, enabling them
to regulate traffic between the two networks. For this example the active router is using
Network Address Translation or NAT to direct traffic from the Internet to a variable number
of real servers on the second layer, which in turn provide the necessary services. Therefore,
the real servers in this example are connected to a dedicated private network segment and
pass all public traffic back and forth through the active LVS router. To the outside world,
the server cluster appears as one entity.
Chapter 7.