Novell LINUX ENTERPRISE 11 - HIGH AVAILABILITY, Руководство пользователя, Страница: 101 / 298

9
Load Balancing with Linux
Virtual Server
The goal of Linux Virtual Server (LVS) is to provide a basic framework that directs
network connections to multiple servers that share their workload. Linux Virtual Server
is a cluster of servers (one or more load balancers and several real servers for running
services) which appears to be one large, fast server to an outside client. This apparent
single server is called a virtual server. The Linux Virtual Server as an advanced load
balancing solution can be used to build highly scalable and highly available network
services, such as Web, cache, mail, FTP, media and VoIP services.
The real servers and the load balancers may be interconnected by either high-speed
LAN or by geographically dispersed WAN. The load balancers can dispatch requests
to the different servers and make parallel services of the cluster appear as a virtual service
on a single IP address, and request dispatching can use IP load balancing technologies
or application-level load balancing technologies. Scalability of the system is achieved
by transparently adding or removing nodes in the cluster. High availability is provided
by detecting node or daemon failures and reconfiguring the system appropriately.
9.1 Conceptual Overview
LVS consists of two main components:
Kernel Code: ip_vs (or IPVS)
The node that runs a Linux kernel patched to include the IPVS code is called direc-
tor. The IPVS code running on the director is the essential feature of LVS.
Load Balancing with Linux Virtual Server 91