Coyote Point Systems was one of the first vendors to produce a commercial load balancer in the mid-Nineties, and the company has always offered good basic features at very competitive prices. The Equalizer E550si is no exception. Starting at $10,995, it is not the least expensive load balancer available, but few of the products with lower price tags have 20 gigabit Ethernet ports or many of the advanced features found in the Equalizer. While it does not have all the features such as compression and traffic acceleration that you'll find in an F5 BIG-IP, Juniper DX, or Citrix NetScaler system (click the links for my reviews), it's also much more affordable. It does offer all the features needed to deliver Web-based applications, including excellent local and geographic load balancing, persistent sessions, SSL termination, and sophisticated health checking.
Initial setup of the system is simple, using a standard serial terminal connection. Setting up virtual clusters and enabling load balancing is also straightforward, because the user interface is clean and easy to navigate. The ease of use reflects the 10-plus years of software development by Coyote Point Systems.
The Equalizer is quite capable. You can set it up between the internal and external networks, with one external server port and 20 internal ports, or inside the firewall with both servers and virtual cluster addresses on the same network. You can establish unlimited numbers of virtual clusters, with up to 128 physical servers in each cluster. The E550si should be able to handle up to 8 million simultaneous users (according to Coyote Point). In my testing, I found that the E550si was able to maintain consistent loads on a variety of servers regardless of the number of rules or persistent connections I created.
Exercising the Equalizer
As for my previous tests of load balancers, I tried out the Equalizer E550si by setting up a virtual cluster of several servers running a demo version of an e-commerce site. I then used an Ixia 400T traffic generator and IxLoad software to simulate a large number of users accessing the virtual Web site, then compared the loads generated on each Web site. The Equalizer was able to keep actual loads on the servers consistent even though their processing power varied considerably. I then enabled a number of features, such as SSL and persistent sessions, and attempted to overload the Equalizer by simulating many concurrent users. As with the other solutions I've tested, this was only possible with artificially small sessions. When simulating actual traffic, the gigabit connection became saturated before the limitations of the device were reached.
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.
Ease of use (20.0%)
Overall Score (100%)
|Coyote Point Equalizer E550si||8.0||9.0||9.0||8.0||9.0|
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