Guest Failover Clustering with VMware

[John Marlin]

First published on MSDN on Jul 26, 2010

This blog discusses running a Windows Server Failover Cluster (WSFC) in a virtual machine (VM) on top of a VMware host.  Running a cluster in a virtualized environment is commonly referred to as "Guest Clustering".  Guest Clustering provides two key values:

1. Application Health Monitoring – Enables health monitoring of applications running within a VM.  For example; if SQL Server is placed in a VM then the health state of SQL will be monitored to ensure it is functional and take recovery actions if the SQL instance were to crash or hang.

2. Application mobility – Allows applications to failover from one VM to another VM.  For example; if you need to patch the guest operating system you can move the application to another VM and reduce downtime.

It is supported by Microsoft to run Failover Clustering in a virtualized environment; however the support policy varies for different guest operating system versions.

Windows NT Server 4.0 / Windows 2000 Server

It is not supported by Microsoft to run a Guest Cluster with the Microsoft Cluster Service (MSCS) on Windows NT Server 4.0 or Windows 2000 Server in any virtualized environment.

Windows Server 2003

For a cluster solution to be supported by Microsoft it must be a tested solution which has been qualified and verified to function properly with the Failover Clustering feature.  The full Windows Server 2003 cluster support policy is documented here: http://support.microsoft.com/kb/309395

When a cluster solution has been qualified it will receive a 'Designed for Microsoft® Windows® Server 2003' logo and be listed on the Windows Server Catalog under "Cluster Solutions".

Two separate VMware configurations have received a logo and are supported in Windows Server 2003 with vSphere 4.0 and EMC storage.  One configuration is with EMC V-Max storage and the other with EMC CLARiiON CX4 storage.  Details can be found here:

· VMware vSphere 4.0 cluster for EMC Symmetrix V-Max

· VMware vSphere 4.0 cluster for EMC CLARiiON CX4

These are the only two supported Windows Server 2003 guest clustering configurations.  The Windows Server 2003 cluster logo program stopped accepting new submissions as of 12/31/09, no additional configurations will be added in the future.

Windows Server 2008 / Windows Server 2008 R2

The Microsoft support policy for Failover Clustering radically changed with Windows Server 2008 to become much more flexible.  The following criteria must be met for a solution to be supported by Microsoft:

1.       On a host Windows Server Failover Cluster all hardware and software components must meet the qualifications to receive the appropriate “Certified for Windows Server 2008” or “Certified for Windows Server 2008 R2” logo.

a.       If a guest cluster is running inside a virtual machine on non-Microsoft hardware virtualization software, the virtual machine must be hosted by a virtualization solution that is listed in the Server Virtualization Validation Program

2.       The solution must not fail any of the tests in the cluster Validation tool.  With virtualized servers in a cluster, run the cluster validation wizard as you would with any other new cluster. The requirement for running the wizard is the same regardless of whether you have a "host cluster" (where failover will occur between two physical computers), a "guest cluster" (where failover will occur between guest operating systems all on the same physical computer), or some other configuration that includes one or more virtualized servers.

It is supported by Microsoft to run Windows Server 2008 and Windows Server 2008 R2 as a guest cluster.  The full support policy is documented here .   In particular see the " Virtualized servers " section.

For more information see the support policy for Microsoft software running in non-Microsoft hardware virtualization soft... .

VMware Considerations

VMware has a Knowledge Base article titled “ Microsoft Cluster Service (MSCS) support on ESX ” which outlines additional support considerations and restrictions.  It is recommended to also review the VMware support policies which have additional considerations.

Please review the "vSphere MSCS Setup Limitations" section in the documentation linked in the VMware KB above for VMware’s complete and authoritative list of configuration restrictions.

Guest Clustering Support Matrix Summary

	ESX 3.5 or earlier	vSphere 4.0	vSphere 4.1 or later
Windows NT Server 4.0	No	No	No
Windows 2000 Server	No	No	No
Windows Server 2003	No	Yes (limited hardware configurations)	No
Windows Server 2008	No	Yes (restricted configurations)	Yes (restricted configurations)
Windows Server 2008 R2	No	Yes (restricted configurations)	Yes (restricted configurations)

Thanks!
Elden Christensen
Senior Program Manager Lead
Clustering & High-Availability
Microsoft