Enhancing availability for outbound clients

You can enhance the availability for client outbound requests by using proxy server arrays. A proxy server array is a group of proxy servers that work together as a single proxy server and share many functions. An array is a good way to increase the availability and performance of your proxy server solution. Arrays share the same Web cache, and distribute the cache across multiple proxy servers that are members of the same array. Arrays also provide fault tolerance because if a single member of the array becomes unavailable, other members of the array are able to act on the failed member's behalf.

The following paragraph describes the functionality of the proxy array. As shown in the illustration below, proxy arrays distribute Web content across all proxy servers in the array so that if a server fails, the remaining servers in the array will continue to service client requests. Proxy Server client requests are sent to the array and then routed to the appropriate proxy server within the array in order to retrieve cached content.

In order to establish proxy arrays, you will need to specify which proxy servers make up the array and ensure that all members of the array meet the following criteria:

1. They belong to the same Active Directory domain and site
2. They have the same proxy array name specified

Note: It is important to note that the Proxy Server configuration information for all of the servers on the array is stored in Active Directory.
Question: What are the two criteria that all members of an array must meet?
Answer: 1) They belong to the same Active Directory domain and site. 2) They have the same proxy array name specified.

As you consider configuring proxy arrays, you will have the option to specify arrays with one server or multiple servers. Your choice will depend on your system requirements. A proxy array can be specified with only one proxy server to:

1. Allow the Proxy Server configuration information to be stored in Active Directory
2. Establish an array that you will extend in the future

Opting to use multiple servers has particular benefits relating to failover. When a proxy server within an array fails, the cached Web content stored on the failed server is lost. Other proxy servers within the array automatically retrieve the lost Web content. By specifying that multiple proxy servers belong to the same array, you can:

1. Distribute the Proxy Server Web content cache
2. Provide immediate failover in the event of a failure

In the next lesson, you will learn how to use proxy arrays to enhance availability for inbound clients.

Click the Exercise link below to check your understanding of how to establish proxy arrays.
Enhancing Availability Outbound Clients - Exercise