Cluster-Aware Updating Overview


Applies To: Windows Server 2012 R2, Windows Server 2012

This topic provides an overview of Cluster-Aware Updating (CAU), a feature for failover clusters that was introduced in Windows Server 2012. For newer info, see Cluster-Aware Updating in Windows Server 2016.

CAU automates the software updating process on clustered servers while maintaining availability. This topic describes scenarios and applications for using CAU, and provides links to content that describes how to integrate CAU into other IT automation and management processes.

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CAU is related to but is distinct from the following foundational technologies:

Feature description

CAU is an automated feature that enables you to update clustered servers with little or no loss of availability during the update process. During an Updating Run, CAU transparently performs the following tasks:

  • Puts each node of the cluster into node maintenance mode

  • Moves the clustered roles off the node

  • Installs the updates and any dependent updates

  • Performs a restart if necessary

  • Brings the node out of maintenance mode

  • Restores the clustered roles on the node

  • Moves to update the next node

For many clustered roles (formerly called clustered applications and services) in the cluster, the automatic update process triggers a planned failover, and it can cause a transient service interruption for connected clients. However, in the case of continuously available workloads such as Hyper-V with live migration or file server with SMB Transparent Failover, CAU can coordinate cluster updates with no impact to the service availability.


The CAU feature is only compatible with Windows Server 2012 R2 and Windows Server 2012 failover clusters and the clustered roles that are supported on those versions.

Practical applications

  • CAU reduces service outages in clustered services, reduces the need for manual updating workarounds, and makes the end-to-end cluster updating process more reliable for the administrator. When the CAU feature is used together with continuously available cluster workloads, such as continuously available file servers (file server workload with SMB Transparent Failover) or Hyper-V, the cluster updates can be performed with zero impact to service availability for clients.

  • CAU facilitates the adoption of consistent IT processes across the enterprise. You can create Updating Run Profiles for different classes of failover clusters and then manage them centrally on a file share to ensure that CAU deployments throughout the IT organization apply updates consistently, even if the clusters are managed by different lines-of-business or administrators.

  • CAU can schedule Updating Runs on regular daily, weekly, or monthly intervals to help coordinate cluster updates with other IT management processes.

  • CAU provides an extensible architecture to update the cluster software inventory in a cluster-aware fashion. This can be used by publishers to coordinate the installation of software updates that are not published to Windows Update or Microsoft Update or that are not available from Microsoft, for example, updates for non-Microsoft device drivers.

  • CAU self-updating mode enables a “cluster in a box” appliance (a set of clustered physical machines running Windows Server 2012, typically packaged in one chassis) to update itself. Typically, such appliances are deployed in branch offices with minimal local IT support to manage the clusters. Self-updating mode offers great value in these deployment scenarios.

Important functionality

Following is a description of important CAU functionality:

  • A user interface (UI) and a set of Windows PowerShell cmdlets that you can use to preview, apply, monitor, and report on the updates

  • An end-to-end automation of the cluster-updating operation (an Updating Run), orchestrated by one or more Update Coordinator computers

  • A default plug-in that integrates with the existing Windows Update Agent (WUA) and Windows Server Update Services (WSUS) infrastructure in Windows Server 2012 R2 or Windows Server 2012 to apply important Microsoft updates

  • A second plug-in that can be used to apply Microsoft hotfixes, and that can be customized to apply non-Microsoft updates

  • Updating Run Profiles that you configure with settings for Updating Run options, such as the maximum number of times that the update will be retried per node. Updating Run Profiles enable you to rapidly reuse the same settings across Updating Runs and easily share the update settings with other failover clusters.

  • An extensible architecture that supports new plug-in development to coordinate other node-updating tools across the cluster, such as custom software installers, BIOS updating tools, and network adapter or host bus adapter (HBA) updating tools.

CAU can coordinate the complete cluster updating operation in two modes:

  • Self-updating mode For this mode, the CAU clustered role is configured as a workload on the failover cluster that is to be updated, and an associated update schedule is defined. The cluster updates itself at scheduled times by using a default or custom Updating Run profile. During the Updating Run, the CAU Update Coordinator process starts on the node that currently owns the CAU clustered role, and the process sequentially performs updates on each cluster node. To update the current cluster node, the CAU clustered role fails over to another cluster node, and a new Update Coordinator process on that node assumes control of the Updating Run. In self-updating mode, CAU can update the failover cluster by using a fully automated, end-to-end updating process. An administrator can also trigger updates on-demand in this mode, or simply use the remote-updating approach if desired. In self-updating mode, an administrator can get summary information about an Updating Run in progress by connecting to the cluster and running the Get-CauRun Windows PowerShell cmdlet.

  • Remote-updating mode For this mode, a remote computer that is running Windows Server 2012 R2, Windows Server 2012, Windows 8.1 or Windows 8, which is called an Update Coordinator, is configured with the CAU tools. The Update Coordinator is not a member of the cluster that is updated during the Updating Run. From the remote computer, the administrator triggers an on-demand Updating Run by using a default or custom Updating Run profile. Remote-updating mode is useful for monitoring real-time progress during the Updating Run, and for clusters that are running on Server Core installations of Windows Server 2012 R2 or Windows Server 2012.

Hardware and software requirements

CAU can be used on all editions of Windows Server 2012 R2 and Windows Server 2012, including Server Core installations. For detailed requirements information, see CAU: Requirements and Best Practices.

To use CAU, you must install the Failover Clustering feature in Windows Server 2012 R2 or Windows Server 2012 and create a failover cluster. The components that support CAU functionality are automatically installed on each cluster node.

To install the Failover Clustering feature, you can use the following tools:

  • Add Roles and Features Wizard in Server Manager

  • Add-WindowsFeature Windows PowerShell cmdlet

  • Deployment Image Servicing and Management (DISM) command-line tool

For more information, see Install or Uninstall Roles, Role Services, or Features.

You must also install the CAU tools, which are included in the Failover Clustering Tools (which are also part of the Remote Server Administration Tools, or RSAT). The CAU tools consist of the CAU UI and the CAU Windows PowerShell cmdlets. You must install the Failover Clustering Tools as follows to support the different CAU updating modes: