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 2, Linux Virtual Server Overview.