Collocated servers
Load Balancer can reside on the same machine as a Web server to which it is distributing incoming requests. This is commonly referred to as collocating a server. Collocated servers keep initial costs down but allow evolving to a more complex configuration, such as a dedicated server for Dispatcher or even a high availability solution. Collocation is also supported for CBR, but only when using bind-specific Web servers and bind-specific Caching Proxy.
Collocation applies to the Dispatcher and Site Selector components.
In a Windows 2000 environment, you can collocate Dispatcher, when using the Dispatcher's NAT and cbr forwarding methods, but it is not supported when using Dispatcher's MAC forwarding method.
Note: To use collocated servers in a Linux environment, apply an arp patch which varies for the different kernel versions of Linux. For details on what you need to apply, refer to the Edge Components InfoCenter at: http://www.ibm.com/software/webservers/appserv/doc/v51/ec/infocenter/inde x.html Select the Load Balancer Administration Guide from the left hand pane. The Administration Guide is displayed in the right pane. Scroll down to the "Requirements for Linux" section. Here you find a link called "Installing the Linux kernel patch (to suppress arp responses on the loopback interface)" which contains detailed information for this issue. |
Figure 4-4 Dispatcher collocated topology
Note: A collocated Web server competes for resources with Load Balancer during times of high traffic. However in the absence of overloaded machines, using collocated servers offers a reduction in the total number of machines necessary to set up a load-balanced site. |
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