My good friend and colleague, Matt Hester, recently wrote a great article on Hyper-V Host Clustering as part of our latest article series, Become a Virtualization Expert in 20 Days! In this article, I’ll build on Matt’s cluster scenario to walk through the advantages and implementation steps for another type of clustering in a Hyper-V environment: Virtual Machine Guest Clustering. Along the way, we’ll explore some new features in Windows Server 2012 Failover Clustering that enhance Virtual Machine Guest Clustering: Virtual Fibre Channel SANs, Anti-Affinity and Virtual Machine Monitoring.
Virtual Machine Guest Clustering allows us to extend the high availability afforded to us by Windows Server 2012 Failover Clustering directly to applications running inside a set of virtual machines that are hosted on a Hyper-V Host Cluster. This allows us to support cluster-aware applications running as virtualized workloads.
While the Hyper-V Host cluster can be running either Windows Server 2012 or our FREE Hyper-V Server 2012 enterprise-grade bare-metal hypervisor, Virtual Machine Guest Clustering requires a full copy of Windows Server 2012 to be running inside each clustered Virtual Machine.
Great question! By clustering both between Hyper-V Hosts and within Virtual Machine Guests, you can improve your high availability scenarios by providing superfast failover during unplanned outages and improved health monitoring of the cluster services.
As Matt pointed out in his article, Hyper-V Host Clusters alone do provide a highly available virtualization fabric for hosting virtual machines, but if a host is unexpectedly down, the VM’s that were running on that host need to be restarted on a surviving host in the cluster. In this scenario. because VMs are completely restarted on the surviving host, the failover time includes the time it takes for the operating system and applications inside each VM to startup and complete initialization.
When virtualizing cluster-aware applications inside VMs, failover times can be dramatically reduced in the event of an unplanned outage. When using Virtual Machine Guest Clustering, cluster-aware applications can more quickly failover by moving just the active application workload without the requirement of restarting entire virtual machines. In addition, many cluster-aware applications, such as Continuously Available File Share Clustering and SQL Server 2012 AlwaysOn, provide managed client-side failovers without any end-user interruption to the application workloads or the need to restart client applications.
Absolutely! You can use both types of clustering together to match your organization’s recovery time objectives ( RTO ) for business-critical application workloads. I generally recommend building the foundation for a resilient and scalable host server fabric by first deploying Hyper-V Host Clustering. This provides a standard base-level of platform high availability for all virtual machines deployed to the host cluster, regardless of whether the application workloads inside each VM support clustering. Then, for business-critical application workloads that are cluster-aware, you can enhance your availability strategy by also leveraging Virtual Machine Guest Clustering for those specific applications inside each VM.
Lots of common applications can be leveraged with Virtual Machine Guest Clustering. In fact, as a general rule-of-thumb, if an application supports Windows Server Failover Clustering, it will be supported as part of a Virtual Machine Guest Cluster. Common application workloads with which I’ve seen particular value when configured as a Virtual Machine Guest Cluster include:
Much like a physical host cluster, Virtual Machine Guest Clusters should have separate network paths for internal cluster communication vs client network communications. At a minimum, each VM in a Guest Cluster scenario should have 2 virtual network adapters defined, with the option for a third virtual network adapter if using shared iSCSI storage ( see the next section for more information on shared storage ). Separate Virtual Networks for VM Guest Clustering Each virtual network to which a VM Guest Cluster node is attached should be consistently configured across all Hyper-V hosts with the same name and set as an “external” virtual network in the Virtual Switch Manager within Hyper-V Manager. This will allow the VMs to communicate over these networks regardless of the host on which a VM is placed.
Tip: On the virtual network adapters to be used for internal cluster communications, do not configure an IP default gateway. This will cause the cluster service to prefer this network adapter for internal cluster communications when both virtual adapters are available.
Most clustered applications required shared storage that is accessible across all cluster nodes – whether those nodes are physical nodes, or in this case, virtual machines. To expose shared storage to clustered applications within virtual machines, two common approaches can be used in Windows Server 2012:
Fibre Channel Storage – New in Windows Server 2012 is the ability to also leverage Fibre Channel storage within Virtual Machine Guest Clusters, supported by the new Virtual Fibre Channel HBA capabilities in Windows Server 2012 and our FREE Hyper-V Server 2012.
Virtual Fibre Channel support in Windows Server 2012 leverages Fibre Channel HBAs and switches that are compatible with N_Port ID Virtualization ( NPIV ). NPIV is leveraged by Windows Server 2012 Hyper-V and the FREE Hyper-V Server 2012 to define virtualized World Wide Node Names ( WWNNs ) and World Wide Port Names ( WWPNs ) that can be assigned to virtual Fibre Channel HBAs within the settings of each VM. These virtualized World Wide Names can then be zoned into the storage and masked into the LUNs that should be presented to each clustered Virtual Machine.
To use Virtual Fibre Channel in Windows Server 2012 Hyper-V or the FREE Hyper-V Server 2012, you can follow these steps:
Completed! Once you’ve completed these steps for each Hyper-V Host and VM that will participate in the Virtual Machine Guest Cluster, you should now have storage that you can format and leverage as shared storage within your cluster!
Another great question! To ensure availability of the overall Virtual Machine Guest Cluster, consider these additional settings to help ensure that the VMs being used as part of the same VM Guest Cluster are placed on separate Hyper-V Hosts for best overall availability:
This month, my fellow Technical Evangelists and I are writing a new blog article series, titled Become a Virtualization Expert in 20 Days! Each day we’ll be releasing a new article that focuses on a different area of virtualization as it relates to compute, storage and/or networking. Be sure to catch the whole series at:
After you’re done reading the series, if you’d like to learn more and begin preparing for MCSA certification on Windows Server 2012, join our FREE Windows Server 2012 “Early Experts” online study group for IT Pros at:
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