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Apéndice A. Uso de LVS con Red Hat Cluster

Puede utilizar el enrutador LVS con un cluster de Red Hat para implementar un sitio de comercio electrónico de alta disponibilidad que proporciona balanceo de carga, integridad de datos y disponibilidad de aplicaciones.
The configuration in Figura A.1, “LVS with a Red Hat Cluster” represents an e-commerce site used for online merchandise ordering through a URL. Client requests to the URL pass through the firewall to the active LVS load-balancing router, which then forwards the requests to one of the Web servers. The Red Hat Cluster nodes serve dynamic data to the Web servers, which forward the data to the requesting client.
LVS with a Red Hat Cluster

Figura A.1. LVS with a Red Hat Cluster

Serving dynamic Web content with LVS requires a three-tier configuration (as shown in Figura A.1, “LVS with a Red Hat Cluster”). This combination of LVS and Red Hat Cluster allows for the configuration of a high-integrity, no-single-point-of-failure e-commerce site. The Red Hat Cluster can run a high-availability instance of a database or a set of databases that are network-accessible to the Web servers.
Una configuración de tres capas es requerida para proporcionar contenido dinámico. Mientras una configuración LVS de dos capas es apta para servidores de web que sirven únicamente contenido estático (que consiste de cantidades pequeña de datos que no cambian frecuentemente) pero no es apta para servidores de web que sirven contenido dinámico. El contenido dinámico puede incluir inventario de productos, ordenes de adquisición o bases de datos de clientes que deben ser consistentes en todos los servidores web para asegurar que los clientes tengan acceso actualizado y correcto a los datos.
Cada capa proporciona las siguientes funciones:
  • Primera capa — los enrutadores LVS ejecutan balance de carga para distribuir solicitudes de web.
  • Segunda capa — Un grupo de servidores web que procesan la solicitud.
  • Tercera capa — Un Red Hat Cluster para servir datos a los servidores de Web.
In an LVS configuration like the one in Figura 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. The active load-balancing router forwards the requests to the set of Web servers.
Each Web server can independently process an HTTP 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.