4. Hardware/Network Requirements

An LVS cluster consists of one or two LVS routers and a collection of real servers providing Web and FTP services. The connection and hardware requirements are described below.

4.1. LVS Routers

A Linux server that will be the primary LVS router is required. This machine needs two network adapters, one connecting it to the public network and the other to a private network of real servers.

If you want failover capability, a second Linux server that will be the backup LVS router is required. This machine also needs two network adapters connecting it to the public network and to the private network of real servers. The adapter devices must match on the two LVS routers. Thus, if devices eth0 and eth1 on the primary LVS router connect it to public and private network, respectively, then these same devices on the backup LVS router must connect it to the public and private network. Note that the backup LVS router is a purely hot standby machine.

4.2. Real Servers

The private network to which the LVS routers are connected includes a variable number of Web/FTP server hosts. Jobs addressed to virtual servers are redirected to these real servers, which may be any kind of computing platform running any operating system or Web server.

During configuration, you assign a weight to each real server. This is an integer reflecting each server's processing capacity (based on memory, processor speed, number of processors, etc.) relative to that of the others. It is the ratio (2/1, 20/10, 200/100) that is significant. For example, a weight of 2000 assigned to a server indicates that it has twice the computing power of a server assigned a weight of 1000. The assigned weight, which may be dynamically adjusted based on load information, is used by two available job scheduling algorithms (described in Table 1). You should be prepared to assign accurate weights.