Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Guida di Installazione Scaricare il pdf (Pagina 55)

Each tier provides the following functions:

First tier — LVS routers performing load-balancing to distribute Web requests.

Second tier — A set of Web servers to serve the requests.

Third tier — A Red Hat Cluster to serve data to the Web servers.

In an LVS configuration like the one in Figure A.1, “LVS with a Red Hat Cluster”, client systems issue

requests on the World Wide Web. For security reasons, these requests enter a Web site through a

firewall, which can be a Linux system serving in that capacity or a dedicated firewall device. For

redundancy, you can configure firewall devices in a failover configuration. Behind the firewall are LVS

load-balancing routers, which can be configured in an active-standby mode. T he active load-balancing

router forwards the requests to the set of Web servers.

Each Web server can independently process an HT T P request from a client and send the response

back to the client. LVS enables you to expand a Web site's capacity by adding Web servers behind the

LVS routers; the LVS routers perform load balancing across a wider set of Web servers. In addition, if a

Web server fails, it can be removed; LVS continues to perform load balancing across a smaller set of

Web servers.

Red Hat Enterprise Linux 4 Virtual Server Administration

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Red Hat LINUX VIRTUAL SERVER 4.7 - ADMINISTRATION Guida di Installazione Pagina 55