Load Balancers

With a hardware appliance--depending on the number of servers you're load balancing--consider whether the load balancer can also take the place of an edge switch. Foundry Networks' load balancers, for instance, provide additional ports you can use for edge switching, so you don't need a separate switch. That's not the case with Coyote Point Systems' and NetScaler's load balancers, which have a limited number of ports (usually one for management, one for LAN connectivity and one for WAN connectivity), so you need a switch as well. A device that does switching can help reduce the long-term management costs of your load-balancing infrastructure.

If you prefer a hardware load balancer but can't justify the price, consider a combination network device that does even more. A NetScaler switch provides not only load balancing but also caching and SSL VPN functionality, and the Foundry Server Iron XL includes Layer 2/3 access control, giving you basic firewall capabilities in addition to load balancing.

What's What

Depending on your Web server and operating system, a software load balancer may require additional investments. If you run Apache on Linux but want to use Microsoft's Network Load Balancing, you'll need an additional server and OS on your shopping list. If you want to stick with a Microsoft-only infrastructure, Windows Advanced Server comes with Microsoft's Network Load Balancing product. It lists for $3,999.

Apache's mod_backhand module can provide load balancing, but you need to be intimate with Apache's and the module's directives, which is a bit daunting. The mod_rewrite module is popular as a catch-all tool, but if you aren't experienced with it, the price you pay is the long learning curve. Zeus Technologies' Extensible Traffic Manager is another option: Its list price of $7,500 and up is a bit pricey, but it offers capabilities similar to those of a hardware load balancer.Don't forget to factor in the cost of hardware for a software solution. When you add up the costs for the hardware, operating system and load-balancing software, you might find you're spending as much as for a hardware solution. If so, you may need to consider a lower-cost hardware load balancer instead.

On the hardware side, Coyote Point and Foundry Networks both offer load-balancer hardware products with features and price tags well-suited for budget-minded enterprises and small IT shops. Coyote Point's Equalizer ($3,995) offers Web-based configuration and management, so with a little training, you should be able to balance your servers easily. Foundry's ServerIron line includes products under $10,000 that may be an option as well.

Balancing Act

Your Web servers will need Secure Sockets Layer (SSL) support, period. And any kind of information exchange that includes personally identifiable information should go via a secure HTTP session. Many load balancers offer this as a value-add, which will increase the cost of a hardware load balancer. Software load balancers should handle security, but if the volume of traffic gets too heavy, you may need additional hardware and software to compensate for the resource-intensive nature of SSL transactions.

Consider adding other security features to protect your Web servers from attack. Most load balancers offer protection against denial of service attacks, but if you choose a Layer 7-capable product from suppliers like Coyote Point, Foundry, Zeus or NetScaler, you can also set them to protect your Web servers against such virus outbreaks as CodeRed or Nimda.

Weighing in the cost and ease of configuration and management is essential when choosing a load-balancing product. The prices aren't cheap, but if your business relies on your Web presence, the potential cost of downtime is much worse.