System-Level Fault Tolerance (Clustering/Network Load Balancing) - Managing NLB Clusters
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A cluster can be managed using the NLB Manager or the NLB.exe command-line utility. Using the NLB Manager, a node can be added, removed, or suspended from cluster operation to perform maintenance, including hardware or software updates. Because data is not replicated between cluster nodes, any data needs to be replicated manually or by using tools such as Robocopy.exe, which are located in the Windows Server 2003 Resource Kit.
Note - Network activity for NLB clusters can be monitored using the Network Monitor and parsers provided in the Windows Server 2003 Resource Kit. These parsers are called Wlbs_hb.dll and wlbs_rc.dll.
Backing Up and Restoring NLB Nodes
The procedure for backing up and restoring NLB nodes is no different than for standalone servers. An ASR backup should be created after any major server configuration change, and the local disks and system state of each node should be backed up regularly (weekly). An NLB configuration can be restored when the system state of a particular node is restored. If a full node recovery is necessary, the system state and local disks should be restored or an ASR restore should be performed. For detailed backup and restore procedures, refer to Chapters 32 and 33 and follow procedures for backing up and restoring standalone servers.
Performing Maintenance on a Cluster Node
To perform maintenance on an NLB cluster node, the administrator can temporarily remove the node from the cluster, perform the upgrade, and add it back in later. Removing the node from the cluster without affecting user connections requires the use of the drainstop option from the Network Load Balancing Manager. The drainstop option tells the cluster to take this node offline and immediately stop connecting new clients to this node. Existing sessions will remain active until they are all closed. When all the sessions are complete, maintenance can be performed, and the server can be made available in the cluster to start accepting user requests.
To perform maintenance on a cluster node, follow these steps:
Log on to a workstation or server that has the Windows Server 2003 Administrative Tools installed.
Click Start, All Programs, Administrative Tools and right-click Network Load Balancing Manager.
Choose the Run-as option and specify an account that has Administrative permissions on the cluster.
Choose Cluster, Connect to Existing.
In the Host text box, type the IP address or name of the cluster and click Connect.
From the Clusters window, select the cluster you want to connect to and click Finish to connect.
Each node in the cluster should appear with a green background, signifying operational status. Right-click the node to perform maintenance and select Control Host, Drainstop, as shown in Figure 31.22.
Figure 31.22 Selecting the Control Host, Drainstop option.
When the node is draining, it should have a half-red and half-green background, and the drainstop operation result should be listed in the log window. Right-click the draining cluster node and select Host Status.
Refer to the summary status to verify that the node is draining and then click OK to close this window.
After you complete all connections on this node, the node will turn red. Perform any necessary maintenance.
When maintenance is complete, if no reboots are necessary, in the NLB Manager, right-click the node and choose Start. If a reboot is necessary, the node will rejoin the cluster according to Initial Host State settings on the Host property page. Change the Initial Host State settings as necessary to achieve the desired node effect according to the type of maintenance that is being performed.
When the node completes rejoining the cluster, it should have a green background in the NLB Manager window.
Click File, Close to exit the Network Load Balancing Manager utility.
Removing a Node from an NLB Cluster
To remove an existing node from a cluster, follow the steps up to step 10 in the "Performing Maintenance on a Cluster Node" section. Then do the following:
Right-click the node and choose Delete Host.
A warning message pops up stating that this action will remove the node from the cluster. Click the Yes button to remove the node.
Deleting the Entire Cluster
To delete an entire cluster, follow the procedure in the "Performing Maintenance on a Cluster Node" section on each node in the cluster. When all nodes are red, indicating a stopped status, right-click the cluster name and choose Delete Cluster, as shown in Figure 31.23.
Figure 31.23 Deleting a cluster.
 This chapter is from Microsoft Windows Server 2003 Unleashed, by Rand Morimoto, et al. (Sams Publishing, 2004, ISBN: 0672326671). Check it out at your favorite bookstore today.
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