Cluster Scenarios

In deciding whether and how to implement clustering, you first need to understand what problem is being solved and how best to solve it using the available technologies. Then you can make a business case for the particular solution or combination of solutions that best solves the particular problem. This section describes various scenarios and the type of clustering appropriate for each.

Intranet or Internet Functionality

An intranet or Internet server is a prime candidate for an NLB cluster. By enabling an NLB cluster across multiple servers, you provide your site with both redundancy and increased capacity. If a server should fail, the load is distributed transparently among the remaining servers.

Each Web server in the cluster runs its own Web server and accesses only local Web pages. This version is "shared nothing" clustering—there are no shared disks and no shared applications or data, with the possible exception of a common back-end database. NLB clusters are an appropriate and relatively inexpensive way to achieve both redundancy and high availability for your Web site, whether internal or external. Clients that need access to the Web pages are distributed among the servers in the cluster according to the load at each server. What makes this work is that most Web pages change fairly infrequently, allowing manual updates of all Web servers with the same information when you need to make changes.

Mission-Critical Availability

If your business absolutely, positively can't be run without a certain application, you need a highly reliable server to make sure that the application is always available. A server cluster is a good solution in this scenario, providing both high availability and scalability. With a server cluster, you group your critical applications into two groups, one group to a server. All the resources for each group are self-contained on the server, but if either server in the cluster fails, the other picks up the services and applications from the failed server, allowing for continuous availability of critical services and applications.

Server clusters require a substantially greater investment in hardware than NLB clusters. In addition, they aren't suitable for "shared nothing" clustering, because they use a shared disk array to keep resources in sync. When a server fails, the other server picks up the applications that had been running on the failed server. Because the disks are shared, the remaining server has access to the same set of data as the failed server, and thus there's no loss of functionality.

Integrated Windows Clustering

As you can see from the previous example, Windows 2000's clustering model lends itself well to an integrated approach that can help maximize your investment in hardware and resources. An NLB cluster can distribute the load of an essentially static Web or other TCP/IP load, passing specific applications to another cluster, which in turn uses the resources of the server cluster that runs the mission-critical messaging and database servers.



Microsoft Windows 2000 Server Administrator's Companion
Microsoft Windows 2000 Server Administrators Companion
ISBN: 0735617856
EAN: 2147483647
Year: 2003
Pages: 320

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