Overview

You can provide failover protection of caching services on your network by using the following:

• Web server accelerator groups
• Appliance clusters

Web Server Accelerator Groups

Key Functionality

DNS Round-Robin dispenses the multiple IP addresses assigned to a single origin Web server DNS name in a rotating sequence, achieving load balancing and automatic failover protection for the acceleration service.

If the appliances are configured as ICP peers of each other, they automatically share information within the group. See How ICP Hierarchies Work for more information.

Although the following illustration shows the origin Web server on the Internet, it could be on the same network as the DNS server and the Web server accelerator, and the browsers could be on the Web, as shown in How Origin Web Server Acceleration Works.

How a Web Server Accelerator Group Works

NOTE:  Steps shown in reverse color are conditional.

Figure 44

Benefits of Web Server Accelerator Groups

• Deploying multiple Web server accelerators, as described in Figure 44, provides load balancing, thus increasing throughput and performance.
• Having multiple Web server accelerators for a single origin Web server provides failover protection and increases reliability.

For tips and guidelines on setting up Web server accelerator groups, see Appliance Web Server Accelerator Group Setup.

Appliance Clusters

Key Functionality

An appliance cluster is a group of appliances that have been configured with the same cluster definition. The cluser dynamically handles forward, transparent, and reverse proxy services that are defined for the cluster.

How Clusters Work

Figure 45

Key Benefits of Clusters

• Assigning services to a cluster provides failover support for all defined services.
• Distribution of service IP addresses among the appliances is automatically negotiated within the cluster.
• If one of the appliances shuts down for any reason, the service IP addresses that were previously assigned to it are redistributed among the remaining appliances.