As corporate Web sites assume increasingly vital roles for business, guaranteed round-the-clock access for employees and customers is a must. Given the critical nature of the task, the unsophisticated methods often used in the past are insufficient for mission-critical Web servers. Load balancers offer a simple, elegant solution, adding another layer of fault-tolerance to your Web site. To see how well seven leading load balancers do the job, we set them up and tore them down at Network Computing's University of Wisconsin-Madison Real-World Labs®.

To view the Report card.Armed with the knowledge and testing experience gained from our initial testing of products in this category a year ago, we analyzed each solution in depth to see how it can benefit your Web site (see "Web Server Redirectors Balance Your Web Load," www.networkcomputing.com/814/814cn2.html). Of course, performance is a large part of the final analysis, but not necessarily the primary part; this time around, we insisted that vendors provide us with redundant setups in order to properly evaluate every aspect of using the load balancers. When only one load balancer is in action, you add a new single point of failure to your network.

Of the seven load balancers we tested, two are software solutions while the remaining five are hardware-based. The relative benefits and disadvantages of each type can be fuzzy. A software solution allows for more cost-effective updates via code updates and patches as they become available. On the other hand, the underlying technology of hardware solutions will determine the limit of their life spans.

Despite the ability of network administrators and manufacturers to update hardware solutions via OS and system patches, some administrators may feel more comfortable with the complete control of the solution that a software load balancer provides.

In the end, deciding which solution will benefit you most depends to a great extent on your specific network configuration. The number of back-end Web servers often can determine the type of load balancer you'll require. Smaller Web sites can more easily use software load balancers, while larger sites may wish to avoid the server-by-server maintenance associated with software load balancers.

We evaluated each load balancer based solely on its ability to load balance. No hardware- or software-specific issues affected the overall grade.

RND Networks/RADWARE Web Server Director Pro 2xFE 5.12 earned top honors--our Editor's Choice award-- with the most complete, comprehensive configuration and management tools, including its top-notch Config Master management software, intuitive and refined configuration options and outstanding failover options. Coming in a close second was Foundry Networks' ServerIron, a newcomer to the load-balancer field that posted some of the best performance numbers we saw, accompanied by better-than-average management tools and failover options.