The most complete form of load glancing comes in dedicated hardware systems such as Cisco’s Director or web. These systems completely hide a cluster from t e outside world, masking the duster behind a single IP address. The hardware manages the distribution of requests by negotiating with servers in the duster to find one that appears to be most ready to handle a new request. Of all load-balancing approaches, this is the most complex to install and manage but offers the best capabilities for large-scale Web installations. Hardware load balancing offers man)’ advantages, including the best distribution of load across servers, extra security in of network address translation, and the best capability to handle system failures. It is also possible to provide redundancy of the cluster management system, which is generally not possible with software-based solutions. On the other hand, hardware systems genrally don’t handle content replication and tend to be pricey Overview of ClustorCATS The Enterpris edition of ColdFusion Server 4.5 ships with ClusterCATS software.
This is a software-based load-balancing solution integrated into the C ild Fusion eerver environment. ClusterCATS works through URL redirection: Your application server is monitored and requests are redirected to another server in the cluster when load gets too high. This is a fairlybasic form of load balancing but it generally works. The version of bundled in ColdFusion 4.5 is not a full version; it lacks replication capabilities that are available in the full version of ClusterCA TS.
A major disadvantage of the URL redirection approach used by ClusterCATS is that your cluster appears to the end user as a large collection of identical Web servers. When they are redirected to another server, users see the change in the URL of the page displayed in their browser. This contrasts with other solutions, which make the cluster .appear ‘to be one large server with a single IP address. ClusterCATS consists of a server component for Windows NT and Solaris, This component controls how a machine plays its role in the cluster and runs on all machines in the cluster. The ClusterCATS Explorer is a Windows NT-based tool for managing a cluster. This can run on any member of the cluster and is used to create a cluster, add and remove servers from a cluster, define load limitations for clusters, and more. To learn to use the Cluster Cats software, refer to the documentation that comes with
What do you from Here?
We have covered the details of the Cold Fusion Administrator that allows you to manage all aspects of the server’s behavior. This information is essential if you manage a ColdFusion server in addition to simply developing applications for it, In the next chapter, we will cover a topic new to ColdFusion 4.5: the installation and use of Coldfusion for Linux, Until version 4.5, ColdFusion was only available for Windows systems and commercial Unix environments such as Solaris. Allaire has responded to the widespread popularity of Linux as a Web server platform even in larger corporate environments that use other operating systems for the rest of their networks. We will look at the installation and basic management of ColdFusion on Linux systems.