Windows Server 2008 Hyper-V Failover Clustering Options

There are many ways to implement Windows Server Failover Clustering with Hyper-V. I could actually find five unique methods to do it. Some of them will actually not give you a fully fault-tolerant solution, but most of them actually make sense in specific scenarios (even if only for demonstrations). In any case, just trying to understand and differentiate them will probably be a good exercise.

1 – Parent-based Failover Clustering with two physical servers

In this first scenario, probably the most common one, you implement Windows Server 2008 Failover Clustering at the Hyper-V Parent (Host) level. You will need some shared storage, like a Fibre-Channel or iSCSI SAN.

Here is a diagram describing the scenario before a failure:

Here is a diagram describing the scenario after a failure:

As you can see, this can survive the failure of one of the physical servers. In fact, if you have a redundant network and storage infrastructure (not shown above), you can have a truly highly available solution.

Additional details about this solution (including screenshots on how to configure it) are available at http://blogs.technet.com/josebda/archive/2008/04/14/snw-demo-windows-server-2008-core-hyper-v-and-failover-clustering-with-screenshots.aspx

2 – Child-based Failover Clustering with two physical servers

In this second scenario, you implement Windows Server 2008 Failover Clustering at the Hyper-V Child (Guest) level. In this case, your shared storage must be an iSCSI SAN.

Here is a diagram describing the scenario before a failure:

Here is a diagram describing the scenario after a failure:

This one can also survive the failure of one of the physical servers. Given redundant network and storage infrastructure (not shown above), you can again have a truly highly available solution.

3 – Mixed Physical/Virtual Failover Clustering

This third scenario is probably is one of the more unusual ones, but I have been asked about it at least a couple of times. Here you have a physical server clustered with a virtual one. If the physical server fails, the virtual sibling will take over the workload. This scenario uses dissimilar hardware with Failover Clustering, but if this is running Windows Server 2008, you can likely make it work. Just make sure you run the Failover Clustering Validation Wizard to confirm this is supported in your specific configuration. In this case, because you need to expose the LUNs directly to the child partition, your shared storage must again be an iSCSI SAN.

Here is a diagram describing the scenario before a failure:

Here is a diagram describing the scenario after a failure:

This can also survive the failure of one of the physical servers. If you configure the network and storage infrastructure to be fault tolerant (not shown above), you can have yet another truly highly available solution.

4 – Failover Clustering with two child partitions on one physical server

This scenario is also common. Here you have a single physical server running Hyper-V and two child partitions where you run Failover Clustering. If the physical server fails, both (virtual) cluster nodes will fail. Obviously, this is not useful for true high availability, but could be interesting for testing, training or demonstrations. In this case, your shared storage must be an iSCSI SAN.

Here is a diagram describing the scenario before a failure:

Here is a diagram describing the scenario after a failure:

This scenario cannot be made truly highly available even if your network and iSCSI SAN are redundant, since you have the physical server running Hyper-V as a single point of failure. The simulated failure can be achieved by turning off one of the child partitions in Hyper-V.

5 – Standalone demo laptop with Virtual iSCSI SAN

This last scenario is something I also get asked a lot. The goal here is to have a single laptop hosting an entire Failover Clustering demo with Hyper-V. In order to accomplish this, you need a virtual iSCSI SAN plus two child partitions to play the role of cluster nodes. To be the virtual iSCSI SAN, you can use an evaluation version of the Microsoft iSCSI Software Target described at http://blogs.technet.com/josebda/archive/2008/01/07/installing-the-evaluation-version-of-wudss-2003-refresh-and-the-microsoft-iscsi-software-target-version-3-1-on-a-vm.aspx. This is certainly not a true highly available solution, but it can be an interesting demo machine with no external network dependencies.

Here is a diagram describing the scenario before a failure:

Here is a diagram describing the scenario after a failure:

As with the previous scenario, this one cannot be made truly highly available, for obvious reasons. In fact, this one only really makes sense for demonstrations or training. The simulated failure can once again be achieved by turning off one of the child partitions in Hyper-V.

Conclusion

I hope this helped you understand the different options for using Failover Clustering with Hyper-V. Note also that you can combine some of these solutions, like the first and the second (some VMs using parent-based and some using child-based failover clustering).

For production use, it’s probably wise to restrict yourself to the first two scenarios. However, if you have a Hyper-V capable laptop and some free time, I would encourage you to try out the last one. Although not a supported production solution, it will certainly teach you a lot about all the technologies involved…

Links 

Additional information about Windows Server 2008 Failover Clustering support
http://support.microsoft.com?id=943984

Failover Clustering support in previous versions of Windows Server
http://support.microsoft.com/?id=309395.

Step-by-Step Guide to Getting Started with Hyper-V
http://www.microsoft.com/downloads/details.aspx?FamilyID=bcaa9707-0228-4860-b088-dd261ca0c80d&DisplayLang=en

Step-by-Step Guide for Testing Hyper-V and Failover Clustering
http://www.microsoft.com/downloads/details.aspx?FamilyId=CD828712-8D1E-45D1-A290-7EDADF1E4E9C&displaylang=en

Failover Cluster Step-by-Step Guide: Configuring a Two-Node File Server Failover Cluster 
http://technet2.microsoft.com/windowsserver2008/en/library/adbf1eb3-a225-4344-9086-115a9389a2691033.mspx

Additional details on Storage Options for Hyper-V
http://blogs.technet.com/josebda/archive/2008/02/14/storage-options-for-windows-server-2008-s-hyper-v.aspx 
http://blogs.technet.com/josebda/archive/2008/03/06/more-on-storage-options-for-windows-server-2008-s-hyper-v.aspx.