Editor's Note: Each month, this column discusses various aspects of the advanced administration of Web applications and e-business sites. This month's column examines Microsoft Application Center 2000, a Microsoft .NET Enterprise Server that manages and deploys servers in a Web farm.
Microsoft Application Center 2000 is a set of tools and services that lets you manage a farm of IIS Web servers as if they were one machine. In Application Center, the concept of grouping servers to facilitate managing them as a whole is called an Application Center server cluster. With Application Center, you can create clusters or add and remove member servers to and from existing clusters.
After you've defined an Application Center server cluster, you can automatically deploy new content to the cluster group as a whole, configure load balancing, and monitor cluster performance. (See "Managing a Web Farm with Application Center 2000," February 2001, for information about installing Application Center and configuring an Application Center server cluster.) This month, I introduce you to Content and Configuration Synchronization—Application Center's ability to automatically synchronize both online content and server configuration settings when you update them, either at a scheduled time interval or manually at any time.
Content and Configuration Synchronization Uncovered
Application Center synchronization is the replication from the controller to each Application Center server cluster member of Web content, COM+ applications, virtual sites (and their associated Internet Server API—ISAPI—filters), global ISAPI filters, files (e.g., .html, .asp, images), and configuration settings. Synchronization ensures that all synchronized content is identical across the cluster and that the time and date settings on each member match the settings on the controller. When you add a new member to a cluster, Application Center automatically synchronizes the member with the controller. Application Center has three synchronization modes:
Automatic (incremental). When you add or update synchronized content on the cluster controller, Application Center immediately replicates the changes to each member in the synchronization loop. This process is analogous to an incremental backup in Microsoft SQL Server except that instead of scheduled incremental backups, Application Center immediately replicates content that you add or change on the Application Center cluster controller.
Full (periodic). Application Center automatically performs a complete synchronization of the members in the synchronization loop at regular intervals to ensure that the content on each server is identical to the controller. This process occurs regardless of when you last updated content. This process is analogous to a full backup in SQL Server at scheduled periods (e.g., every night).
Manual (full or partial). You can manually synchronize the entire cluster, specific members, or specific applications at any time. This process is analogous to performing a manual, on-demand full backup of a SQL Server database.
Application Center uses the concept of applications, which are collections of resources (e.g., Web site content, components) that are synchronized as a whole. Figure 1 shows the applications on my system. Application Center synchronization uses single-controller synchronization to deploy and synchronize Web and Microsoft .NET or Microsoft Windows DNA applications. In single-controller synchronization, you can designate only one cluster member as the controller at a time, and the controller is the authoritative source of all content and settings. Application Center doesn't deploy Win32 applications such as Microsoft Office: You need Microsoft Systems Management Server (SMS) or Active Directory (AD) to deploy Win32 applications.
At the heart of configuration, COM+, and ISAPI synchronization is Windows Management Instrumentation (WMI). By definition, WMI is an OS interface through which components can provide information and notification. WMI enables Application Center to perform powerful operations, such as deploy and monitor a COM+ component remotely.