Load balancing in Windows Server 2003

This overview of Microsoft Windows Server 2003’s Network Load Balancing Manager appears compliments of Tech Toolshed, a new resource dedicated to creating first-rate, affordable references for today’s technology professionals. Lockergnome readers receive a special 20-percent discount on any purchase of $30 or more from Tech Toolshed. The information included here comes from Essential Guide: Windows Server 2003 Administration Fundamentals, a comprehensive PDF reference.

Network load balancing (NLB), which is included in all editions of Windows Server 2003, provides a means to distribute TCP/IP traffic across multiple servers. For instance, you could use NLB to distribute Web site clients to multiple servers hosting individual copies of the site. Windows Server 2003 introduced the Network Load Balancing Manager, a tool you can use to configure and manage load-balanced clusters from a single location.

What’s the difference between load balancing and clustering?
Before considering what the Network Load Balancing Manager offers, it’s important to understand the difference between the NLB service and the Cluster Service. The NLB service provides a means for load balancing TCP/IP traffic among multiple servers in an NLB cluster. The servers participating in the NLB cluster do not share storage or other resources, but instead run their own instances of the load-balanced applications. For i, each server would run IIS with an instance of the same Web site, but each would be a separate copy. NLB simply manages the incoming traffic and balances it out to the servers participating in the cluster.

NLB provides no failover capability, but the Cluster Service does provide redundancy and failover capability. Servers in this type of cluster generally share common storage and function as a single, logical unit. By contrast, an NLB cluster is a group of individual servers working independently to process the traffic that the NLB service passes their way. Essentially, the NLB service enables all servers in the NLB cluster to be addressed by a single IP address. You can combine NLB clustering with Cluster Service clusters, but these two cluster types must remain separate; that is, a server can’t participate in both types of clusters. The usual solution is to build an NLB cluster upstream to service a Cluster Service cluster.

What Network Load Balancing Manager can do
The Network Load Balancing Manager is a stand-alone management application (not an MMC console snap-in) that you use to create and manage NLB clusters from a single management point. It’s installed by default when you install Windows Server 2003. You can also run the Network Load Balancing Manager on a Windows XP workstation by installing the Windows Server 2003 Administration Pack, available from Microsoft’s Web site. To install the Administration Pack on Windows XP, you must have installed Service Pack 1 or hot fix QFE Q329357 on the Windows XP Professional computer.

The Network Load Balancing Manager enables you to accomplish the following tasks:

• Create new NLB clusters — You use the Network Load Balancing Manager to create an NLB cluster and add the first host to it.
• Add hosts to an existing NLB cluster — You can enable NLB on a network interface through the properties for the interface in the Network Connections folder. Enabling NLB in this way requires a trip to the server or a remote management solution. The Network Load Balancing Manager lets you enable NLB remotely while adding the host to the NLB cluster.
• Remove hosts from an existing NLB cluster — The Network Load Balancing Manager makes it possible to remove a host from an existing NLB cluster and automatically remove NLB from the host’s network configuration remotely.
• Configure all properties for individual cluster hosts and the cluster itself — You can configure properties for individual hosts such as unique host ID, dedicated IP address, and initial NLB state. You can also perform cluster-wide management such as adding cluster IP addresses and defining port rules.
• Replicate the cluster configuration to other hosts — Replicating the configuration to other hosts simplifies configuration when adding new hosts to the cluster.
• Perform diagnostics and view statistics for NLB clusters — The Network Load Balancing Manager displays its log at the bottom of the window, and you can also open a dialog with status information for each host.
• Manage hosts in the cluster — You can start, stop, suspend, and resume a host. You can also drainstop a host, which allows the host to finish processing all pending requests prior to stopping the NLB service.

Here’s a list of common tasks and how to accomplish them using the Network Load Balancing Manager:

• Create a new cluster: Choose Cluster, New to start the new cluster wizard.
• Add a host to an existing cluster: Select the cluster and choose Cluster, Add Host.
• Change the cluster virtual IP address: Select the cluster, choose Cluster, Properties, and set IP address on the Cluster Parameters tab.
• Add virtual IP addresses to the cluster: Select the cluster, choose Cluster, Properties, and add addresses on the Cluster IP Addresses tab.
• Manage (start, stop, etc.) the NLB service on all hosts in a cluster: Select the cluster and choose Cluster, Control Hosts.
• Configure port rules for the cluster: Select the cluster and choose Cluster, Control Ports.
• Change a host’s priority in the cluster: Select the host, choose Host, Properties, and set priority on the Host Parameters tab.
• Manage the NLB service on a single host: Select the host and choose Host, Control Host.
• Save the list of hosts connected in NLB Manager: Choose File, Save Host List.
• Connect to a cluster to manage it: Choose Cluster, Connect To Existing, enter name of host in the cluster, click Connect, choose a host, and click Next.