|Red Hat Cluster Suite: Configuring and Managing a Cluster
|Chapter 6. Introduction to Linux Virtual Server
While Red Hat Enterprise Linux can be configured in a variety of different ways, the configurations can be broken into two major categories:
High-availability clusters using Red Hat Cluster Manager
Load-balancing clusters using Linux Virtual Servers
This part explains what a load-balancing cluster system is and how to configure a load-balancing system using Linux Virtual Servers on Red Hat Enterprise Linux.
To an outside user accessing a hosted service (such as a website or database application), a Linux Virtual Server (LVS) cluster appears as one server. In reality, however, the user is actually accessing a cluster of two or more servers behind a pair of redundant LVS routers that distribute client requests evenly throughout the cluster system. Load-balanced clustered services allow administrators to use commodity hardware and Red Hat Enterprise Linux to create continuous and consistent access to all hosted services while also addressing availability requirements.
An LVS cluster consists of at least two layers. The first layer is composed of a pair of similarly configured Linux machines or cluster members. One of these machine acts as the LVS routers, configured to direct requests from the Internet to the cluster. The second layer consists of a cluster of machines called real servers. The real servers provide the critical services to the end-user while the LVS router balances the load on these servers.
For a detailed overview of LVS clustering, refer to Chapter 7 Linux Virtual Server Overview.