The more I study and use Microsoft Application Center 2000, the more its features amaze me. Application Center 2000 is one of the .NET servers (along with Exchange 2000 Server, SQL Server 2000, Commerce Server 2000, BizTalk Server 2000, Host Integration Server 2000, and Internet Acceleration Server 2000). Although Application Center 2000 is a 1.0 product, many of the technologies that form the product's backbone aren't new; they're simply borrowed or transferred (and enhanced) from older server products in the Microsoft suite. In this article, I discuss Content and Configuration Synchronization, Application Center 2000's ability to automatically synchronize both online content and server configuration settings when they're automatically or manually updated. At the synchronization's heart is Content Replication System (CRS), a lightning-quick file-transfer technology first publicly introduced in Microsoft Site Server but used internally in Redmond for many years. "CRS is kind of like a very efficient and very fast FTP but with the ability to retain ACLs so you don't lose security (in the form of file permissions) in the process. And it has an API," Brad Wright, a lead CRS architect, once told me.
Application Center 2000 synchronization is the replication, across an Application Center 2000 cluster from the controller to each cluster member, of Web content, COM+ applications, virtual sites (and their associated ISAPI filters), global ISAPI filters, files (e.g., HTML, ASP, and images), and configuration settings. Synchronization ensures that all synchronized content is identical across the cluster and that each member's time and date settings match the controller's settings. When a new member is added to a cluster, it's automatically synchronized with the controller.
Application Center defines applications as collections of resources (e.g., Web site content, components) that are synchronized as a whole. Application Center synchronization focuses on deploying and synchronizing Web and Microsoft Windows Digital Networking Architecture (DNA) applications and uses single-controller synchronization, in which only one cluster member can be designated as the controller or master at one 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 do that.
You should note two things. First, Application Center Content and Configuration Synchronization doesn't automtically deploy or synchronize COM components and COM+ applications. They must be manually deployed to each cluster member using the Deployment Wizard. Second, global ISAPI filters also must be manually deployed to the cluster controller using the Deployment Wizard. The ISAPI filters will be synchronized with the members when their Web services are restarted.
Application Center 2000 has three synchronization modes:
- Automatic (incremental): When synchronized content is added to or updated on the cluster controller, the changes are immediately replicated to each member in the synchronization loop.
- 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 content on the controller. This synchronization occurs regardless of when content was last updated.
- Manual (full or partial): You can manually synchronize the entire cluster, specific members, or specific applications at any time.
I think you'll agree that deploying Web applications into Web farms is one of the IIS administrator's most challenging duties; just keeping Web farm content updated and synchronized is tough. Application Center 2000 can dramatically help you deploy and synchronize Web application content and configurations.
