Server Virtualization Series: Your Hyper-V Hosts and Clustering an Availability Story (Part 13 of 20) by Matt Hester

When deploying multiple Windows Server 2012 Hyper-V hosts into an environment, High Availability should be one of the things an IT Pro needs to take into account.  If one Hyper-V host fails, it is no longer just one server or application that goes down, it is probably at least 5 (or 100) depending on how many VMs are running on a given Hyper-V host.  To achieve High Availability, you should consider using the Failover Clustering capability built into Windows Server 2012 to provide automatic failover should one of your Hyper-V hosts fail.  If you are not familiar with this capability, then you definitely should take some time and read the article from Matt where he goes into detail on clustering Hyper-V hosts.

I am including a brief snippet directly from Matt’s post below.  For the full article, please visit Matt’s post directly.

One of the features in Windows Server 2012 that got greatly enhanced is the Failover Clustering. See the bottom of this post for a list of all the new and improved features. In today’s part we are going to take a look at how Hyper-V takes advantages of some of these enhancements and how you can use Failover Clustering and Hyper-V to truly beef up your virtualization environment. With Hyper-V there are two ways you can cluster your environment. You can cluster the Hyper-v hosts systems or you can cluster the hyper-v guest systems. Specifically in today’s post we are going to look at Hyper-V hosts and how they can be clustered. Tomorrow Keith is going to take a look at how the guest (virtual servers) take advantage of clustering.

When you begin to think about clustering your Hyper-V servers at a basic level, think of Hyper-V as another application that supports being clustered. With Hyper-V being the program that is clustered and the all the other files (vhd’s, snapshots, settings) as just a part of the story. In this regard clustering hyper-v works in a similar fashion to SQL or SharePoint, and the process to cluster them is generally the same. When you cluster the hosts, you get a lot of benefits:

  • Avoids a single point of failure when consolidating
  • Survive Host Crashes
    • VMs restarted on another node
  • Restart VM Crashes
    • VM OS restarted on same node
  • Recover VM Hangs
    • VM OS restarted on same node
  • Zero Downtime Maintenance & Patching
    • Live migrate VMs to other hosts
  • Mobility & Load Distribution
    • Live migrate VMs to different servers to load balance

With our Live Migration support in Hyper-V we do not limit the amount of concurrent live migrations. This is important especially if you have large clustered environments and with the scalability you can up to 8,000 virtual machines per cluster. Aidan Finn did a great little test on concurrent live migrations: Windows Server 2012 Hyper-V Concurrent Live Migration & NIC Teaming Speed Comparisons. One last note about failover and clustering, while this post focuses on using Windows Server 2012, failover clustering is also supported in our FREE Microsoft Hyper-V Server 2012. You can learn more about Hyper-V server here: 31 Days of Our Favorite Things: Get Happy over the Free Hyper-V Server 2012 (Part 9 of 31)

So where do you begin? Before you can begin the installation you will need to verify some pre-requisites for your servers. Here is some of the pre-requisites (for a full list take a look here:Failover Clustering Hardware Requirements and Storage Options

  • imageServers: We recommend that you use a set of matching computers that contain the same or similar components. This is especially important when you start to migrate virtual machines from server to another. One note if your servers are different make sure you check the processor compatibility in your virtual machine settings. Your virtual machine will need to be turned off to configure this setting.
  • Network adapters and cable (for network communication): For these environments and if your going to do a lot of migrations, you will want to with 10GbE. This is the way to go and also in the network infrastructure that connects your cluster nodes, avoid having single points of failure.
  • Device controllers or appropriate adapters for the storage: Serial Attached SCSI or Fibre Channel or iSCSI. Remember Windows Server 2012 has built in iSCSI services and can be a cost effective storage solution.
  • Storage: You must use shared storage that is compatible with Windows Server 2012. In Windows Server 2012 you can use shared storage that is attached, and you can also use SMB 3.0 file shares as shared storage for Hyper-V servers that are configured in a failover cluster. For more information on this take a look at this article: 31 Days of Our Favorite Things- SMB 3.0 the Glue in Windows Server 2012.

Taking time to verify you meet these requirements will save you time through validation of your cluster. After you have verified the pre-requisites you can then install Hyper-V and Failover Clustering on all servers in your cluster. The installation of these services is standard and straight forward. Just one note, remember Hyper-V is located in roles and Failover Clustering is locating in features when you go through the Add Roles and Features wizard

Harold Wong

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