By Jeffrey Witt
Though Web sites represent virtual worlds, there's still plenty of physical infrastructure behind these electronic presences. The RadWare WSD-Pro+ belongs to a category of products referred to as load balancers, the unsung building blocks in the foundation of any Web server farm. The WSD-Pro+ distributes the flow of incoming traffic across servers, creates a redundancy scheme, and offers easy scalability.
On our tests, we positioned the WSD-Pro+ in front of our two Windows NT servers running Microsoft's IIS Web Server and the same content. The WSD-Pro+ model we tested offers two Fast Ethernet ports for attaching the unit to Internet access routers and to a switch for connections to the servers. As the term load balancer implies, data packets or requests that arrive to your site are parceled out across your servers.
Though this allows for increased performance in terms of response time, it also means you can skip expensive hardware upgrades by scaling up your Web farm with additional machines. Since the WSD-Pro+ can represent content of multiple servers with a single virtual address, you have a cost-effective method of incrementally building your site. For large-scale sites looking for ultimate performance, RadWare claims a 445-Mbps throughput rate for HTTP traffic.
The WSD-Pro+ is easy to set up. Through a standard terminal connection, you assign an IP and routing addresses, as well as additional identification information. The management utility then takes over configuration of the box.
The ConfigMaster software is a Java-based SNMP management tool that gives a graphical representation of the WSD-Pro+, showing real-time port status and offering pull-down menus for configuring and monitoring the device. The software can run in standalone mode or through a browser and stands out by making a complicated process simple.
Adding or replacing servers doesn't require network or server reconfiguring, since the WSD-Pro+ uses a virtual IP address to talk to the server cluster. You have a choice of load-balancing methods for directing traffic. For Windows NT-only servers, a load-balancing algorithm is available based on Microsoft's built-in SNMP agent.
You can direct traffic to specific servers based on their processing power and define distribution thresholds. For narrowing requests even further, you can use the SuperFarm attribute, which lets you send users to specific servers that contain only certain file types.
All your site's information is kept secure via the access controls of RadWare's Facility for Access Control and Security (FACS). The number of sessions a server accepts can be limited to avoid hacker attacks such as SYN Flood. As an additional security measure, the Network Address Translation (NAT) feature represents the server farm to the outside world with the single IP address of the WSD-Pro+.
In a world where a downed Web site is akin to a "Closed" sign on the door of your business, the WSD-Pro+ creates bulletproof fault tolerance. By continuously monitoring the servers, the WSD-Pro+ can automatically redirect users to available resources without interruption of service in the case of failure.
For ultimate protection, the WSD-Pro+ can even back itself up. We added a twin unit to see this feature in action. The two units use a technique referred to as state mirroring to update one another, allowing for transparent failover. The units can run in tandem for optimum performance (as opposed to having one unit sitting idly in standby mode). For physical Web site redundancy, you can configure an agent to direct traffic to an entirely different location in case of total loss of service.
In terms of management, ConfigMaster plugs into HP OpenView for Windows and provides SYSlog messages that a large variety of network management tools can interpret. From the ConfigMaster console, there are any number of graphically represented statistics. You can view Elements (general performance specifications, such as requests and responses) as well as application- or server-specific information.
As you collect data, you can easily display the information in graphs in real time or saved to file. Being able to monitor exactly what's going on with your server farm during peak loads is handy for determining the number of clients attached to different servers, so you can direct traffic to minimize connection failures.
The WSD-Pro+'s plug-in appliance approach doesn't disrupt your network layout and contains excellent management tools. Reasonably priced, the product gives ISP and large- site performance features and around-the-clock availability to anyone's Internet beachhead.