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Configuring Host Clusters in VMM to Support Highly Available Virtual Machines

Updated: January 14, 2010

Applies To: Virtual Machine Manager 2008, Virtual Machine Manager 2008 R2, Virtual Machine Manager 2008 R2 SP1

This topic explains how to configure and manage host clusters in System Center Virtual Machine Manager (VMM) 2008 and System Center Virtual Machine Manager 2008 R2 to support highly available virtual machines (or HAVMs).

To avoid downtime for virtual machines on a host when that host fails or requires maintenance, you can configure failover clusters of two or more hosts. If one node of the cluster fails, virtual machines on that host automatically are migrated to, and start running on, another node in the cluster. Support for host clusters, therefore, ensures high availability for virtual machines on hosts in that cluster.

noteNote
The focus of this topic is host clusters that are failover clusters created in Windows Server 2008 or Windows Server 2008 R2, for which VMM is fully cluster-aware. VMM also supports host clusters created in VMware VirtualCenter. For information about adding VMware host clusters to VMM and managing the virtual machines on clustered ESX Server hosts in VMM, see Managing a VMware Infrastructure in VMM.

Creating and Configuring a Host Cluster for VMM

This section explains the tasks you must perform to create and configure a host cluster for VMM. The following tasks are required:

  1. Create a Failover Cluster in Windows Server 2008 or Windows Server 2008 R2.

  2. Configure Highly Available Storage for the Cluster.

  3. Add the host cluster to VMM.

  4. Configure Common Virtual Networks on All Nodes in VMM.

  5. Optionally Enable PRO for the Host Cluster in VMM.

1. Create a Failover Cluster in Windows Server 2008 or Windows Server 2008 R2

Failover clustering is a feature of Windows Server 2008 Enterprise Edition and Windows Server 2008 Datacenter Edition, and of Windows Server 2008 R2 Enterprise Edition and Windows Server 2008 R2 Datacenter Edition. Before you can add a host cluster to VMM, you must use Failover Cluster Management in Windows Server 2008 or Windows Server 2008 R2 to create the cluster. Windows Server 2008 supports as many as 16 nodes in a single cluster.

Before you create the cluster, you must run the Validate a Configuration Wizard by using Failover Cluster Management to ensure that the configuration of your servers, networks, and storage meets a set of specific requirements for failover clusters. For more information, see Hyper-V: Using Hyper-V and Failover Clustering (http://go.microsoft.com/fwlink/?LinkId=128066).

VMM support for Windows Server 2003 server clusters is less extensive than its support for Windows Server 2008 and Windows Server 2008 R2 failover clusters. VMM does not recognize a Windows Server 2003 server cluster, so you must add each node of the cluster to VMM individually, and VMM treats each clustered host just like a non-clustered host. You cannot use VMM to create or quick migrate highly available virtual machines that can be placed on Windows Server 2003 server clusters. Nevertheless, if any highly available virtual machine on a Windows Server 2003 server cluster, created outside VMM, fails over from one host to another, VMM detects and correctly reports the virtual machine on the new host.

noteNote
VMM 2008 and VMM 2008 R2 can also manage highly available virtual machines on clustered VMware ESX Server hosts. The host cluster must be created in VMware VirtualCenter. To add a VMware host cluster to VMM, you add the VirtualCenter server that is managing the cluster to VMM. For more information, see Managing a VMware Infrastructure in VMM.

Network Requirements

Unlike standalone hosts in VMM, host clusters must be in an Active Directory domain that has a two-way trust relationship with the domain that contains the VMM server.

The following network configurations are not supported for host clusters:

  • Untrusted Active Directory domain

  • Perimeter network—A perimeter network is a collection of devices and subnets placed between a private network and the Internet to protect the private network from unauthorized users. A perimeter network also is known as a screened subnet or DMZ.

noteNote
VMM supports managing clustered hosts in a disjointed namespace, which occurs when one or more domain member computers have a primary Domain Name Service (DNS) suffix that does not match the DNS name of the Active Directory domain of which the computers are members. For example, a member computer that uses a primary DNS suffix of corp.contoso.com in an Active Directory domain named na.corp.contoso.com is using a disjointed namespace.

Before you can add a host cluster in a disjointed namespace to a VMM server that is not in a disjointed namespace, you must add the DNS suffix for the host cluster to the TCP/IP connection settings on the VMM server.

2. Configure Highly Available Storage for the Cluster

To deploy highly available virtual machines on a host cluster, you must first configure shared storage for the clustered hosts.

VMM 2008 R2 supports the following enhancements to storage for HAVMs, which are available for Hyper-V host clusters created in Windows Server 2008 R2:

  • Clustered Shared Volume (CSV) Support—VMM 2008 R2 supports the Windows Server 2008 R2 clustered shared volume (CSV) feature. CSV enables all hosts on a Windows Server 2008 R2 failover cluster to concurrently access virtual machine files on a single shared logical unit number (LUN). Because all nodes on the cluster can access a single shared LUN, virtual machines have complete transparency with respect to which node actually owns a LUN. This enables multiple highly available virtual machines to share the same LUN but still migrate independently without affecting other HAVMs that are sharing the same LUN.

    noteNote
    VMM 2008 does not support using cluster disks formatted with clustered file systems. In VMM 2008, any HAVMs that share a LUN are imported into VMM with Unsupported Cluster Configuration status. To resolve this issue, use Failover Cluster Management to reconfigure the virtual machines to have their own LUNs. Then, in the VMM Administrator Console, use the Repair action with the Ignore option to refresh each virtual machine’s status in VMM.

    Customers who are migrating to VMM 2008 R2 and want to consolidate their existing virtual machines in a single cluster shared volume (CSV) LUN can use the new quick storage migration feature to migrate storage of a running virtual machine to a different host or a different location on the same host with minimal downtime and no loss of state. In Virtual Machines view of the VMM Administrator Console, use the Migrate storage action. For more information, see How to Migrate Storage of Virtual Machine Files. Within a managed VMware infrastructure, VMM will use VMware Storage VMotion if it is available.

  • Support for HAVMs on cluster disks with a Clustered File System—VMM 2008 did not support creating or managing HAVMs on cluster disks with a Clustered File System (CFS). VMM 2008 R2 can be used to create and manage HAVMs on failover clusters that use cluster disks created with a third-party solution such as Melio File System 1.5 from Sanbolic. Melio File System is a clustered file system designed for SAN storage environments and provides shared access to data on a SAN from multiple servers.

  • Support for storage class resources—VMM 2008 supports creating HAVMs only on a Physical Disk resource type in a failover cluster. VMM 2008 R2 extends this support to any storage class resource, such as Veritas Storage Foundation 5.1 for Windows (SFW). SFW is an online storage management solution for creating virtual storage devices from physical disks and arrays. Volumes created as part of a cluster resource group by using SFW are detected by VMM 2008 R2 and can be selected during virtual machine placement or migration. An SFW volume is limited to one virtual machine.

  • SAN Migration in and out of clustered hosts—VMM 2008 R2 supports the use of SAN transfers to migrate virtual machines and highly available virtual machines between host clusters, to a host cluster from a non-clustered host, and from a host cluster to a non-clustered host. When you migrate a virtual machine into a cluster from a non-clustered host by using a SAN transfer, VMM checks all nodes in the cluster to ensure that each node can see the LUN and automatically creates a cluster disk resource for the LUN. Even though VMM automatically configures the cluster disk resource, it does not validate it. You must use the Validate a Configuration Wizard in Failover Cluster Management to validate the newly created cluster disk resource. To migrate a virtual machine from a host cluster to a non-clustered host by using a SAN transfer, the virtual machine must be on a dedicated LUN that is not using CSV.

For information about specific SAN configuration requirements for VMM, see Configuring a SAN Environment for VMM. For general information about storage requirements for failover clusters in Windows Server 2008, see Add Storage to a Failover Cluster (http://go.microsoft.com/fwlink/?LinkId=128068).

3. Add the Host Cluster to VMM

After creating the failover cluster in Windows Server 2008 or Windows Server 2008 R2, add the host cluster to VMM in order to start managing it in VMM. In the VMM Administrator Console, use the Add Hosts Wizard and specify either the name of the cluster or name of any node in the cluster. VMM discovers all nodes of the failover cluster, enables the Hyper-V role in Windows Server if needed, and adds the host cluster to VMM.

Alternatively, you can use the Add-VMHostCluster cmdlet in the Windows PowerShell – Virtual Machine Manager command shell to add the host cluster to VMM.

For more information, see How to Add a Host Cluster to VMM (http://go.microsoft.com/fwlink/?LinkID=162794).

ImportantImportant
To successfully add a cluster that was created in Windows Server 2008 to VMM, all nodes of the cluster must be powered on and connected to the network. This is not required for clusters created in Windows Server 2008 R2.

VMM cannot manage more than one cluster that has the same cluster name. If you attempt to add a host cluster under the same name as an existing host cluster in VMM, the action will not complete successfully. This can occur if you add a VMware VirtualCenter Infrastructure 3 (VI3) environment that has a host cluster with the same name as an existing host cluster of Hyper-V hosts, or if VMM is managing multiple VI3 environments that have clusters with the same name.

4. Configure Common Virtual Networks on All Nodes in VMM

To avoid loss of network connections for virtual machines when they are migrated within a host cluster, configure common virtual networks that have the same name on all hosts in the cluster. In VMM 2008, virtual networks are recognized as common virtual networks only if the cases of all letters in the network names match. This restriction was removed in VMV 2008 R2. When it identifies common virtual networks, VMM 2008 R2 does not evaluate the case of the letters in the network names.

If an HAVM uses a virtual network that is not common to all hosts in the cluster, the virtual machine is placed in an Unsupported Cluster Configuration state.

You should create your virtual networks before placing highly available virtual machines on clustered hosts. Changes to the network topology after you deploy the virtual machines might result in HAVMs temporarily losing network connectivity.

To view the common virtual networks that are configured on all nodes in the cluster, in the VMM Administrator Console, display the Networks tab in the host cluster properties. To bind the virtual network adapter to virtual networks on the clustered hosts, use the Networking tab in the host properties.

For information about configuring virtual networks for Hyper-V hosts, and a procedure for configuring virtual networks on a host, see How to Add or Modify Virtual Networks on a Host (http://go.microsoft.com/fwlink/?LinkId=163453).

5. Optionally Enable PRO for the Host Cluster in VMM

Performance and Resource Optimization (PRO) is available for hosts and virtual machines in host clusters that are managed by VMM 2008 or VMM 2008 R2. PRO supports workload- and application-aware resource optimization within a virtualized environment based on performance and health data provided by PRO-enabled management packs in System Center Operations Manager 2007 SP1 or System Center Operations Manager 2007 R2. PRO can recommend or automatically implement remedial actions, through PRO tips, to minimize downtime and accelerate time to resolution.

PRO-initiated remediation actions can include migrating virtual machines within a host cluster to load-balance CPU and memory usage on the clustered hosts. If you have a mission-critical application that is not suitable for migration, you can exclude the virtual machine on which the workload is running from host-level actions in PRO. If the host exceeds its CPU or memory threshold, the virtual machine will not be migrated even if it is using the largest amount of that resource. Even if you exclude an HAVM from host-level PRO actions, you will receive PRO tips for right-sizing the virtual machine’s configuration.

For more information about PRO, see About PRO.

Managing Host Clusters

Some management activities for host clusters must be performed outside VMM. You must configure, validate, and create the failover cluster outside VMM. Node additions or removals also need to happen outside VMM. After adding or removing a node, you must follow up in VMM by adding or removing the VMM agent.

Disk Management

You must configure, add, or remove the clustered disks outside VMM. After you make external changes to the disks, refresh the host cluster in VMM to update the disk configurations.

In VMM 2008 R2, when you migrate a virtual machine into a cluster from a non-clustered host by using a SAN transfer, VMM checks all nodes in the cluster to ensure that each node can see the LUN and automatically creates a cluster disk resource for the LUN. Even though VMM automatically configures the cluster disk resource, it does not validate it. You must use the Validate a Configuration Wizard in Failover Cluster Management to validate the newly created cluster disk resource. To migrate a virtual machine out of a cluster to a non-clustered host, the virtual machine must be on a dedicated LUN that is not using the Cluster Shared Volume (CSV) feature of Windows Server 2008 R2.

To find out which disks are available for creating highly available virtual machines, in the VMM Administrator Console, display the Storage tab in the host cluster properties. This tab provides a central location for finding shared storage that is available to the clustered hosts and how much disk space is available.

Adding or Removing Clustered Hosts

To add or remove a clustered host from a host cluster, you must add or evict the node from the failover cluster outside VMM and then perform the following tasks according to whether the cluster node was added or evicted:

  • Cluster node added—When a node is added to a host cluster outside VMM, VMM discovers the new node and displays it in VMM Administrator Console under its host cluster. The node has Pending status until you add it to VMM as a host. Until you add the host in VMM, if any highly available virtual machine on any other node in the host cluster fails over to the new node, the virtual machine has Missing status in VMM. Use the Add host action to add the host to VMM. For more information, see How to Add a Pending Host to VMM.

    noteNote
    After you add a node to an existing Hyper-V host cluster and add the host to VMM, you will need to set the default remote connection port on the new host to port 2179, the remote connection port that Hyper-V uses. The property is on the Remote tab of the Host Properties dialog box.

  • Cluster node removed—VMM detects when a node is evicted from a host cluster outside VMM. In that case, VMM begins managing the host as a stand-alone host in the parent host group for the host cluster. If you don’t want to continue to manage the host as a stand-alone host, use the Remove host action to remove the host from VMM. For more information, see How to Remove a Host (http://go.microsoft.com/fwlink/?LinkID=121827).

    If you evict a node from a host cluster that has PRO enabled and you want to continue to use PRO on the host, you must manually configure at least one default virtual machine path on the host for use during virtual machine placement. To specify default virtual machine paths, use the Placement tab in the Host Properties dialog box. For more information, see How to Set Placement Options for a Host.

Removing a Host Cluster from VMM

To remove a host cluster from VMM, use the Remove host cluster action in Hosts view or Virtual Machines view of the VMM Administrator Console. VMM discovers all hosts in the cluster and removes the VMM agent from them. VMM does not destroy the failover cluster in Windows Server 2008 or Windows Server 2008 R2, and you can continue to manage the highly available virtual machines on the cluster by using Hyper-V and Failover Cluster Management.

If the failover cluster for a host cluster is destroyed outside VMM, and you want to continue to manage the hosts in VMM, you will need to remove the host cluster from VMM and then add the hosts again as stand-alone hosts.

See Also

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