Microsoft Cluster Service support on vSphere (iSCSI)

Lately a customer asked me about Microsoft Cluster Service support on a vSphere iSCSI environment.

The  VMware Documentation for vSphere and vSphere Update 1 states:

Before you set up MSCS, review the list of functionality that is not supported for this release, and any requirements and recommendations that apply to your configuration. The following environments and functionality are not supported for MSCS setups with this release of vSphere:

– Clustering on iSCSI, FCoE, and NFS disks. 

It wasn’t clear however if this also affects a Microsoft Cluster that is created with an iSCSI initiator running inside the guest OS. I’ve contacted VMware Support on this case and they told me:

We don’t support iscsi for mscs even if the software initiator in run from within windows, or with any other method. Technically you might be able to get it to work but you will have an unsupported setup if you ever hit any issues. As such I cannot recommend you go down this route.

So we can conclude that within vSphere, Microsoft Cluster Service (Failover Clustering) isn’t supported on iSCSI, FCoE and NFS no matter what the configuration looks like.

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  1. Steve Burkett

     /  March 29, 2010

    We fell in to this trap recently in our virtualisation project. Our external consultant’s hadn’t flagged up VMware’s lack of MSCS support on iSCSI SAN’s till after we’d started racking up our new HP Lefthand gear. Microsoft seem to support MSCS on Hyper-V with iSCSI, so why’s VMWare dragging their feet?

  2. Hi Steve,

    Maybe this is due to the possible fact that is hasn’t been fully tested. I really have no other clue.


  3. this post is very usefull thx!

  4. Tony

     /  July 15, 2010

    we actually have to windows 2003 VMs running MSCS using the windows iscsi initiator that connect directly to the SAN.

    the share a volume of 200G for MS SQL 2005 clustering functionality.

    so far so good, no problem at all….it’s implemented on prod enviroment for sharepoint.


  5. Well I wasn’t stating that it doesn’t work since we did some testings as well and it did work. However the official support statement was it isn’t supported in vSphere 4.0

  6. Helar

     /  September 12, 2010

    Tony, did you use RDM or just software iSCSI from the guest? Is there a recommended setup?

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