Synchronization Fundamentals

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In the context of Microsoft Application Center 2000 (Application Center), synchronization is replication of content and configuration settings from the cluster controller to one or more cluster members (see the following list). Synchronization ensures that all synchronized content is identical across the cluster. When you add a new member, it is automatically synchronized with the controller; that is, if you select the Include this member in synchronizations check box in the Add New Member Wizard or use the command-line command AC CLUSTER /ADD without the /NOSYNCADD parameter.

Deployment is the transfer, from one cluster (usually a stager) to another cluster (usually the production cluster), of content and configuration settings. Synchronization is the transfer of content and configuration settings from the cluster controller to one or more cluster members. Other than this distinction, the processes and resources that are used are identical to synchronization and the difference is merely a semantic one. You can synchronize and deploy content by using the Application Center snap-in, the New Deployment Wizard, or AC DEPLOY from the command line.

You can use Application Center to synchronize or deploy:

  • Web sites, virtual directories (and their associated ISAPI filters), and Active Server Pages (ASP) applications.

  • COM+ applications (see the following Notes).

  • Global ISAPI filters (see the following Notes).

  • File system directories and files.

  • Exportable certificates.

  • Certificate Trust Lists (CTLs).

  • Data Source Names (DSNs).

  • Microsoft® Windows® Management Instrumentation (WMI) monitoring settings (in the Application Center namespace, Microsoft Health Monitor 2.1 settings, and event filters).

  • Application Center monitors (listed in the Synchronized Monitors data group).

  • Registry keys.

  • Metabase (Internet Information Services 5.0 [IIS] configuration) settings.

To facilitate synchronization and deployment, Application Center uses applications, which are a collection of resources that are synchronized as a whole. Application Center synchronization is focused on the deployment and synchronization of Web applications and applications based on the .NET platform. Application Center does not synchronize or deploy applications such as Microsoft Office or system upgrades, such as a Service Pack (SP). You must use another method to perform these tasks (for example, Microsoft Systems Management Server).

Application Center uses single-controller synchronization, where only one cluster member can be designated as the controller at one time and the controller is the authoritative source of all synchronized content and settings. Additionally, Application Center is based on shared-nothing clustering, where each cluster member has a full set of the content and settings and can function on its own; that is, there are no shared resources, such as a Redundant Array of Inexpensive Disks (RAID).

Bb687399.note(en-us,TechNet.10).gif Notes

Automatic Updates

Application Center provides two types of automatic synchronization. You can use the following automatic updates to keep content and configuration settings consistent across your cluster without needing to intervene:

  • Change-based synchronization—Application Center receives notification if synchronized content (except for COM+ applications, CAPI store information, Access Control List [ACL] changes, and network settings) on the cluster controller changes. The files that are changed are updated automatically and immediately on all cluster members in the synchronization loop. You can disable change-based synchronization in the cluster_name Properties dialog box by clearing the Synchronize members when content is updated check box.

  • Interval-based synchronization—periodically, Application Center synchronizes all Application Center applications to ensure that the content and configuration settings are identical across the cluster. You can set the interval between full synchronizations in the cluster_name Properties dialog box. The synchronization interval is set to 60 minutes by default. You can disable interval-based synchronization in the cluster_name Properties dialog box by clearing the Synchronize members when content is updated check box or by using the command-line command AC DEPLOY /DISABLESYNC.

On-Demand Synchronization

Application Center provides three types of manual synchronization. You can use the following types of on-demand synchronization to control when and how synchronization takes place within a cluster:

  • Cluster synchronization—all cluster members in the synchronization loop are synchronized with the controller. All applications are synchronized (except for COM+ applications).

  • Member synchronization—only the specified cluster member is synchronized with the controller. All applications (except for COM+ applications) are synchronized. This type of synchronization occurs whether the member is in the synchronization loop or not.

  • Application synchronization—the specified application is synchronized with the cluster controller on every member in the synchronization loop.

Advanced Synchronization and Deployment

This type of synchronization provides granular control over which applications, cluster members, and to some extent, which configuration settings are involved. As well, this type is the only type that can be used across cluster boundaries. You can deploy or synchronize specific applications to specific servers and choose whether to include file and folder permissions, COM+ applications, and global ISAPI filters. Additionally, when deploying ISAPI filters or COM+ applications, you can specify the time used for draining user connections before restarting the Web Service on the targets.

The Synchronization Loop

The synchronization loop consists of all cluster members that are enabled for synchronization by selecting the Include this member in synchronizations check box in the member_name Properties dialog box. Cluster members can be taken out of, or brought into, the loop at anytime by using either the command-line utility or the Application Center snap-in. Neither advanced synchronization nor deployment is affected by these synchronization settings and will complete for all available (Alive) members or targets.

Bb687399.note(en-us,TechNet.10).gif Note   Member synchronization can be performed on a member regardless of whether it is in the synchronization loop.

Synchronization loop membership is not the same as the list of members that are serving content (Online). Members that are in the synchronization loop are not necessarily available to serve Web content. This is determined by their Online/Offline status. Members that are online are not necessarily in the synchronization loop.

There are two states that can be problematic:

  • Online and not synchronized—the member continues to serve content that might not be current with the content on other members. The user's experience would be that during one visit to your site they get one set of content (being served by the out-of-date member that is not in the synchronization loop) and, on a subsequent visit, another set of content (being served by a synchronized member).

  • Offline and synchronized—the content on this member is current with the cluster but the member is not serving content.

Synchronization Exclusions

You can select files to exclude from synchronization and deployment. You can exclude individual files, individual folders and their contents, or a particular file type. The exclusions are defined on the targets and apply only to the specific target. These exclusions apply to all synchronizations and deployments to the target.

Synchronizations Between Different File Systems

When synchronizing or deploying between a server with a FAT file system and an NTFS file system, keep the following in mind:

  • FAT to NTFS—synchronization from FAT to NTFS results in synchronization failure and rollback occurs because the ACLs cannot be applied to the FAT file system.

  • NTFS to FAT without ACL synchronization—this should proceed as expected.

  • NTFS to FAT with ACL synchronization—if you synchronize or deploy from a server with a FAT file system to a server with an NTFS file system, the files delivered to the NTFS file system inherit the ACLs from their new parent directories.

Bb687399.caution(en-us,TechNet.10).gif Caution   Installation on FAT16 partitions is not supported (except for Administrative client installations).

Synchronization of Deletions

When synchronizing or deploying applications with resources that have been deleted from the controller, the deletions will be synchronized with the targets. This means that the resources and settings will be removed from the targets.

Synchronizations View

The Synchronizations view provides detailed information about synchronizations and deployments in two sections: a list of all the synchronizations on the cluster and a details view for the selected synchronization. The list includes all synchronizations and deployments for the cluster and all cluster members since the cluster was created. The details pane comprises two parts: a details view and an events list. The details view lists detailed information about the selected synchronization or deployment. The events list comprises all synchronization events for the selected synchronization or deployment.

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