Article

Load balancer selection dos and don'ts

Meredith B. Derby, assistant news editor

Rather than buy bigger and more expensive Web servers, many enterprises need only purchase load balancing equipment, according to IT consultant Tony Bourke. "Load balancers are the muscle that Web sites require," said Bourke, who specializes in networking and load balancing design and implementation. Load balancing is necessary because multiple servers servicing one application can quickly be overwhelmed and crash if the workload is not split up.

Load balancing is a simple technology that provides straightforward results, said Bourke. Choosing the right solution and implementing it correctly, however, requires some homework. To help IT professionals do their homework more efficiently, searchWindowsManageability gathered some class notes from Bourke and Chris Archey, product manager for Seattle, WA-based network load balancing technology developer F5 Networks. Bourke is a private consultant specializing in Unix administration, networking, and load balancing. He has designed and implemented SLB and Unix architectures for many high-profile and high-traffic Web sites. In this story, they offer background information on load balancing and several time-saving technology selection dos and don'ts.

In a nutshell, load balancing divides work between two or more computers. The work gets done in the same amount of time without any one computer getting overloaded. Hardware, software or a combination of both can achieve load balancing.

Load balancing is agentless

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and platform- and protocol-independent, Bourke said. Network-based load balancing even requires no special configuration or clustering because the load balancers sit in front of the servers to divvy up the traffic load.

Companies whose servers are constantly max out at peak usage times may be good candidates for load balancing. Bourke and Archey offer these suggestions about how to determine whether your company needs load balancing technologies and how to choose the right products.

Do understand your needs before you start testing load balancing technologies, Bourke said. Archey recommended asking yourself: "What kind of application is going to be load balanced? How many requests will it receive over time? How much traffic will be expected?"

Do make sure your current network is configured correctly before adding load balancing to the mix. Make a diagram of the network, and be sure you understand the current and prospective configuration, Archey suggested.

Do research, Archey said. Talk to your peers, and read white papers and analyst reports on different vendors' products.

Do understand that "all load balancers are not created equal," according to Archey. Some do some functions better than others. Some include capabilities that you may not need. Further, Bourke said, some load balancers only work in layer two networks, while others only in layer three networks.

Don't let vendors sway you based on what they think is important, Archey said. Know what application you want load balanced, and "make the vendors prove they can support it."

Do ask potential vendors the tough questions, Archey said: "What is your company's health now, and what will it be in the future? What is your standard of support? Do your field support personnel understand networking and load balancing so they can effectively help me?"

Do ensure that the load balancer will be flexible, advised Archey. Is it adequate for today's application, but for future applications, too?

Do look for a load balancer with a similar graphical interface as Windows when deploying in a Windows environment, said Archey. Windows administrators are familiar with certain features, such as installation wizards. A congruent load balancer interface will not require more training.

Don't assume your load balancers are more or less secure than any other device on your network, Bourke said. Most are secure in registering denial-of-service attacks and viruses like Code Red. But, don't hesitate to make configuration changes so that your load balancer can resist other known viruses, said Archey.

Don't forget about secure sockets layer (SSL) acceleration, Archey said. SSL is a protocol used to manage the security of message transactions on the Web (Whatis.com). SSL ensures that applications are secure, but not every load balancer supports it, he said.

Do understand cookie-based resistance, Bourke said. Cookies, information stored on a user's hard drive about that user, can be monitored by load balancers via the unique session ID's the cookies create. This way, customers won't get kicked off the server they've been assigned. In the case of e-commerce, customers' "shopping carts" won't be lost because they will remain on the server initially assigned to them, Bourke said. Not all load balancers have this feature, however.

Do know that while Windows 2000 Server Edition has a built-in load balancer, it is very basic, according to Bourke. It does not have all the features that other vendors' load balancers have, such as cookie-based resistance.

Don't blame the load balancer if your Web site experiences problems or goes down, Bourke stressed. There are many other technologies that make Web sites run. Because load balancing is a relatively simple technology, chances are it's not guilty.

FOR MORE INFORMATION

More links on network load balancing

SearchWindowsManageability has loads of links related to hardware and infrastructure management

Dos and don'ts of choosing, managing clusters


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