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What's New in Failover Clustering in Windows Server 2012

Published: February 29, 2012

Updated: January 13, 2014

Applies To: Windows Server 2012

This topic describes the Failover Clustering functionality that is new or changed in Windows Server 2012. This functionality supports increased scalability, continuously available file-based server application storage, easier management, faster failover, and more flexible architectures for failover clusters.

Failover clusters provide high availability and scalability to many server workloads. These include server applications such as Microsoft Exchange Server, Hyper-V, Microsoft SQL Server, and file servers. The server applications can run on physical servers or virtual machines. In a failover cluster, if one or more of the clustered servers (nodes) fails, other nodes begin to provide service (a process known as failover). In addition, the clustered roles (formerly called clustered services and applications) are proactively monitored to verify that they are working properly. If they are not working, they restart or move to another node. Failover clusters also provide Cluster Shared Volume (CSV) functionality that provides a consistent, distributed namespace that clustered roles can use to access shared storage from all nodes. For an overview of the Failover Clustering feature in Windows Server 2012, see Failover Clustering Overview.

The following table and sections summarize key Failover Clustering functionality in Windows Server 2012 that is new or changed since Windows Server 2008 R2.


Feature/functionality New or improved Description

Cluster scalability


Scales to 64 nodes and 8,000 virtual machines per cluster

Management of large-scale clusters by using Server Manager and Failover Cluster Manager


Provides GUI tools to streamline management and operation of large-scale clusters

Management and mobility of clustered virtual machines and other clustered roles


Helps allocate cluster resources to clustered virtual machines and other clustered roles

Cluster Shared Volumes


Improves CSV setup and enhances security, performance, and file system availability for additional cluster workloads

Support for Scale-Out File Servers


Provides CSV storage and integrates with File Services features to support scalable, continuously available application storage

Cluster-Aware Updating


Applies software updates across the cluster nodes while maintaining availability

Virtual machine application monitoring and management


Extends clustered virtual machine monitoring to the applications that run in the clustered virtual machines

Cluster validation tests


Validates Hyper-V and CSV functionality and performs faster

Active Directory Domain Services integration


Increases cluster resiliency and supports a wider range of deployments

Quorum configuration and dynamic quorum


Simplifies quorum setup and increases the availability of the cluster in failure scenarios

Cluster upgrade and migration


Allows migration of virtual machines from Windows Server 2008 R2, migration to CSVs, and reuse of existing storage

Task Scheduler integration


Integrates Failover Clustering with additional server functionality

Windows PowerShell support


Allows scripting of Failover Clustering functionality that was introduced in Windows Server 2012

Failover clusters in Windows Server 2012 can scale to a greater number of nodes and virtual machines than clusters in Windows Server 2008 R2, as shown in the following table:


Cluster maximum Windows Server 2012 Windows Server 2008 R2




Virtual machines or clustered roles

8,000 (up to 1,024 per node)


Server Manager and Failover Cluster Manager provide new capabilities in Windows Server 2012 to manage large-scale clusters.

Server Manager can discover and manage the nodes of the cluster. It enables remote multi-server management, remote role and feature installation, and the ability to start Failover Cluster Manager from the Server Manager GUI. For more information, see Manage Multiple, Remote Servers with Server Manager.

New Failover Cluster Manager features that simplify large-scale management of clustered virtual machines and other clustered roles include:

  • Search, filtering, and custom views. Administrators can manage and navigate large numbers of clustered virtual machines or other clustered roles.

  • Multiselect. Administrators can select a specific collection of virtual machines and then perform any needed operation (such as live migration, save, shutdown, or start).

  • Simplified live migration and quick migration of virtual machines and virtual machine storage. Live migration and quick migration are easier to perform.

  • Simpler configuration of Cluster Shared Volumes (CSVs). Configuration is a right-click from the Storage pane. CSVs have additional enhancements, which are described in Cluster Shared Volumes, later in this topic.

  • Support for Hyper-V Replica. Hyper-V Replica provides point-in-time replication of virtual machines between storage systems, clusters, and data centers for disaster recovery.

What value do these changes add?

These scalability features in Windows Server 2012 improve the configuration, management, and maintenance of large physical clusters and Hyper-V failover clusters.

In Windows Server 2012, administrators can configure settings, such as prioritize starting or placing virtual machines and clustered roles on cluster nodes, to efficiently allocate resources to clustered workloads. The following table describes these settings:


Setting Description Scope

Priority settings: High, Medium (the default), Low, or No Auto Start

  • Clustered roles with higher priority are started and are placed on nodes before those with lower priority.

  • If a No Auto Start priority is assigned, the role does not come online automatically after it fails, which keeps resources available so other roles can start.

All clustered roles, including clustered virtual machines

Preemption of virtual machines based on priority

  • The Cluster service takes offline lower priority virtual machines when high-priority virtual machines do not have the necessary memory and other resources to start after a node failure. The freed-up resources can be assigned to high-priority virtual machines.

  • When necessary, preemption starts with the lowest priority virtual machines and continues to higher priority virtual machines.

  • Virtual machines that are preempted are later restarted in priority order.

Clustered virtual machines

Memory-aware virtual machine placement

  • Virtual machines are placed based on the Non-Uniform Memory Access (NUMA) configuration, the workloads that are already running, and the available resources on each node.

    The number of failover attempts before a virtual machine is successfully started is reduced. This increases the uptime for virtual machines.

Clustered virtual machines

Virtual machine mobility features

  • Multiple live migrations can be started simultaneously. The cluster carries out as many as possible, and then queues the remaining migrations to complete later. Failed migrations automatically retry.

  • Virtual machines are migrated to nodes with sufficient memory and other resources.

  • A running virtual machine can be added to or removed from a failover cluster.

  • Virtual machine storage can be live migrated.

Clustered virtual machines

Automated node draining

  • The cluster automatically drains a node (moves the clustered roles that are running on the node to another node) before putting the node into maintenance mode or making other changes on the node.

  • Roles fail back to the original node after maintenance operations.

  • Administrators can drain a node with a single action in Failover Cluster Manager or by using the Windows PowerShell cmdlet, Suspend-ClusterNode. The target node for the moved clustered roles can be specified.

  • Cluster-Aware Updating uses node draining in the automated process to apply software updates to cluster nodes. For more information, see Cluster-Aware Updating later in this topic.

All clustered roles, including clustered virtual machines

What value do these changes add?

These features in Windows Server 2012 improve the allocation of cluster resources (particularly when starting or maintaining nodes) in large physical clusters and Hyper-V failover clusters.

Cluster Shared Volumes (CSVs) were introduced in Windows Server 2008 R2 to provide common storage for clustered virtual machines. In Windows Server 2012, CSVs can provide storage for additional clustered roles. CSVs allow multiple nodes in the cluster to simultaneously access the same NTFS file system without imposing hardware, file type, or directory structure restrictions. With CSVs, multiple clustered virtual machines can use the same LUN and still live migrate or quick migrate from node to node independently.

The following is a summary of new CSV functionality in Windows Server 2012.

  • Storage capabilities for a wider range of clustered roles. Includes Scale-Out File Servers for application data, which provide continuously available and scalable file-based (SMB 3.0) server storage for Hyper-V and applications such as Microsoft SQL Server. For more information, see Support for Scale-Out File Servers later in this topic.

  • CSV proxy file system (CSVFS). Provides cluster shared storage with a single, consistent file namespace while still using the underlying NTFS file system.

  • Support for BitLocker Drive Encryption. Allows decryption by using the common identity of the computer account for the cluster (also called the Cluster Name Object, or CNO). This enables physical security for deployments outside secure data centers and meets compliance requirements for volume-level encryption.

  • Ease of file backup. Supports backup requestors that are running Windows Server 2008 R2 or Windows Server 2012 Backup. Backups can use application-consistent and crash-consistent Volume Shadow Copy Service (VSS) snapshots.

  • Direct I/O for file data access, including sparse files. Enhances virtual machine creation and copy performance.

  • Removal of external authentication dependencies. Improves the performance and resiliency of CSVs.

  • Integration with SMB Multichannel and SMB Direct. Uses new SMB 3.0 features to allow CSV traffic to stream across multiple networks in the cluster and leverage network adapters that support Remote Direct Memory Access (RDMA). For more information, see Server Message Block overview.

  • Storage can be made visible to only a subset of nodes. Enables cluster deployments that contain application and data nodes.

  • Integration with Storage Spaces. Allows virtualization of cluster storage on groups of inexpensive disks. The Storage Spaces feature in Windows Server 2012 can integrate with CSVs to permit scale-out access to data. For more information, see Storage Spaces Overview.

  • Ability to scan and repair volumes with zero offline time. Maintains CSV availability while the NTFS file system identifies, logs, and repairs anomalies.

What value do these changes add?

These new features provide easier CSV setup, broader workload support, enhanced security and performance in a wider variety of deployments, and greater file system availability.

What works differently?

CSVs now appear as CSV File System (CSVFS) instead of NTFS.

Scale-Out File Servers can host continuously available and scalable storage by using the SMB 3.0 protocol. Failover clusters in Windows Server 2012 provide the following foundational features that support this type of file server:

  • A Distributed Network Name (DNN), which provides an access point for client connections to the Scale-Out File Servers.

  • A Scale-out File Server resource type that supports Scale-out File Services.

  • Cluster Shared Volumes (CSVs) for storage. For more information, see Cluster Shared Volumes earlier in this topic.

  • Integration with File Services features to configure the clustered role for the Scale-Out File Server.

What value do these changes add?

These features support continuously available and readily scalable file services for applications and for end users. For more information, see Scale-Out File Server for Application Data Overview.

Cluster-Aware Updating (CAU) is an automated feature that allows updates to be applied automatically to the host operating system or other system components in clustered servers, while maintaining availability during the update process. This feature leverages automated draining and failback of each node during the update process. By default, it uses the Windows Update Agent infrastructure as its update source. For an overview of the CAU feature, see Cluster-Aware Updating Overview.

What value does this change add?

CAU provides increased uptime of high availability services, easier maintenance of failover clusters, and reliable and consistent IT processes.

In clusters running Windows Server 2012, administrators can monitor services on clustered virtual machines that are also running Windows Server 2012. This functionality extends the high-level monitoring of virtual machines that is implemented in Windows Server 2008 R2 failover clusters. If a monitored service in a virtual machine fails, the service can be restarted, or the clustered virtual machine can be restarted or moved to another node (depending on service restart settings and cluster failover settings).

What value does this change add?

This feature increases the uptime of high availability services that are running on virtual machines within a failover cluster.

The Validate a Configuration Wizard in Failover Cluster Manager simplifies the process of validating hardware and software across servers for use in a failover cluster. The performance for large failover clusters has been improved and new tests have been added.

The following are improved features related to validation:

  • Improved performance. Runs significantly faster, especially to test storage.

  • Targeted validation of new LUNs. Allows specifying a new LUN (disk), rather than testing all LUNs when validating storage.

  • Integration with WMI. Exposes cluster validation status to applications and scripts through Windows Management Instrumentation (WMI).

  • New validation tests. Provides validation test support for CSVs, and for Hyper-V and virtual machines (when the Hyper-V role is installed).

  • Validation test awareness of replicated hardware. Helps support multisite environments.

What value do these changes add?

The added validation tests help confirm that the servers in the cluster will support smooth failover, particularly of virtual machines from one host to another.

Integration of failover clusters with Active Directory Domain Services (AD DS) is made more robust in Windows Server 2012 by the following features:

  • Ability to create cluster computer objects in targeted organizational units (OUs) or in the same OUs as the cluster nodes. Aligns failover cluster dependencies on AD DS with the delegated domain administration model that is used in many IT organizations.

  • Automated repair of cluster virtual computer objects (VCOs) if they are deleted accidentally.

  • Cluster access only to Read-only domain controllers. Supports cluster deployments in branch office or perimeter network scenarios.

  • Ability of the cluster to start with no AD DS dependencies. Enables certain virtualized data center scenarios.

Failover clusters do not support group Managed Service Accounts.

What value do these changes add?

These features improve the configuration and resiliency of failover clusters.

The following features in Windows Server 2012 enhance the management and functionality of the cluster quorum:

  • Configure Cluster Quorum Wizard. Simplifies quorum configuration and integrates well with new features and existing quorum functionality.

  • Vote assignment. Allows specifying which nodes have votes in determining quorum (by default, all nodes have a vote).

  • Dynamic quorum. Gives the administrator the ability to automatically manage the quorum vote assignment for a node, based on the state of the node. When a node shuts down or crashes, the node loses its quorum vote. When a node successfully rejoins the cluster, it regains its quorum vote. By dynamically adjusting the assignment of quorum votes, the cluster can increase or decrease the number of quorum votes that are required to keep running. This enables the cluster to maintain availability during sequential node failures or shutdowns.

What value do these changes add?

These enhancements simplify quorum setup and increase the availability of the cluster in failure scenarios.

By using the updated Migrate a Cluster Wizard in Windows Server 2012, administrators can migrate the configuration settings for clustered roles (formerly called clustered services and applications) from clusters that are running Windows Server 2012, Windows Server 2008 R2, or Windows Server 2008. Migration enhancements in Windows Server 2012 include:

  • Export and reimport Hyper-V virtual machines.

  • Migrate to CSV disks.

  • Map storage and virtual networks.

  • Reuse existing storage.

What value does this change add?

The Migrate a Cluster Wizard provides ease and flexibility to deploy, upgrade, and migrate failover clusters.

In Windows Server 2012, Task Scheduler is integrated with Failover Clustering to allow the administrator to configure clustered tasks. A clustered task is a Task Scheduler task that is registered on all cluster nodes. Depending on the task, it can be enabled on all or a subset of the nodes.

The administrator can configure clustered tasks in three ways:

  • Cluster-wide. The task is scheduled on all cluster nodes.

  • Any node. The task is scheduled on a single, random node.

  • Resource specific. The task is scheduled only on a node that owns a specified cluster resource.

The administrator can configure and manage clustered tasks by using the following Windows PowerShell cmdlets:

  • Register-ClusteredScheduledTask

  • Set-ClusteredScheduledTask

  • Get-ClusteredScheduledTask

  • Unregister-ClusteredScheduledTask

What value does this change add?

Clustered tasks provide a flexible mechanism to use cluster resources to run applications or processes at predefined times.

To use the Windows PowerShell cmdlets for Failover Clustering, you must install the Failover Cluster module for Windows PowerShell that is included with the Failover Clustering tools. For a complete list of the cmdlets, see Failover Clustering Cmdlets in Windows PowerShell.

New Windows PowerShell cmdlets support capabilities in Failover Clustering in Windows Server 2012 including the following:

  • Manage cluster registry checkpoints, including cryptographic checkpoints.

  • Create Scale-Out File Servers.

  • Monitor virtual machine applications.

  • Update the properties of a Distributed Network Name resource.

  • Create and manage clustered tasks.

  • Create a highly available iSCSI Target Server.

What value does this change add?

The new Windows PowerShell cmdlets provide management and scripting support for the Failover Clustering features in Windows Server 2012.

What works differently?

The Test-ClusterResourceFailure cmdlet replaces Fail-ClusterResource.

  • The Cluster.exe command-line tool is deprecated, but it can be optionally installed with the Failover Clustering tools. Windows PowerShell cmdlets for Failover Clustering provide functionality that is generally equivalent to Cluster.exe commands. For more information, see Mapping Cluster.exe Commands to Windows PowerShell Cmdlets for Failover Clusters.

  • The Cluster Automation Server (MSClus) COM interface is deprecated, but it can be optionally installed with the Failover Clustering tools.

  • Support for 32-bit cluster resource DLLs is deprecated, but 32-bit DLLs can be optionally installed. You should update cluster resource DLLs to 64-bit.

  • The Print Server role is removed from the High Availability Wizard, and it cannot be configured in Failover Cluster Manager.

  • The Add-ClusterPrintServerRole cmdlet is deprecated, and it is not supported in Windows Server 2012.

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