Coyote Point load balancer sticks to the essentials
Equalizer E550si doesn't match the traffic acceleration features of high-end competitors, but delivers most everything else at a winning price
The Equalizer can implement the "sticky," or persistent, sessions required for e-commerce by inserting cookies in the code returned to the client's browser, ensuring that persistence is maintained even if the client's IP address changes or more than one user is coming from the same client IP address, which is typical in these days of network address translation (NAT). Cookie-based persistence ensures that all requests from the client go to the same Web server in the cluster, a necessity in maintaining a connection to the back-end database server or other n-tier application servers.
The Equalizer has sophisticated health-checking capabilities, not just limited to pinging an IP address to see if the server is still responding. It can check specific ports or URLs and match the response received against the correct reaction. You can also set up scripts that execute if an incorrect response is received, or if parameters such as network or processor utilization exceed a given threshold. This means that you can set up dynamic clusters that respond automatically to increases or decreases in load, or automatically bypass failed systems. The Equalizer provides a full set of reports, including historical trends, so that you can see traffic peaks in context rather than as isolated events.
Easy traffic management
The rules-based system allows you to create sophisticated and flexible rules to control how traffic is directed. Rules are easily created using expressions similar to shell scripts, with standard Boolean operators ("and," "or," "not," and so on). This enables you to create rules for handling traffic based on various parameters. For instance, if a client request for a specific URL comes from a certain range of IP addresses, it could be directed to servers A, B, and C, but if it comes from an address outside the range, it could be fed to servers D, E, and F. This functionality is not by any means unique, but it is well documented and easy to use.
The Equalizer has enough power to handle a large Web site or to deliver high-bandwidth Web-based applications in an internal network; 20 gigabit Ethernet ports should provide enough bandwidth to support very large server farms or a wide variety of subnets for security purposes. Because each port can be a separate VLAN, you could put the application servers for sales and marketing on a different subnet from the ERP servers or the Web server farm, for example.
The Equalizer E550si is a great value for the price, with excellent performance and high-bandwidth capabilities. It offers good error detection, health-checking, and load-balancing features, as well as optional geographic load balancing and SSL acceleration. It doesn't provide the compression or session consolidation features you'll find in an F5, Juniper, or Citrix box, but it's much less expensive. The Equalizer should work well for any corporate Web-based applications or Web farms supporting sites less heavily trafficked than, say, Amazon.com. For sites delivering corporate applications internally, where dozens or hundreds of 100-megabit or gigabit connections would be hitting the app simultaneously, a load balancer with compression and application acceleration capabilities, such as Citrix NetScaler or Juniper DX, would be a better choice.