Vmware ESX 5 from a Vcenter

Two Windows 2008 R2 VMs

I am attempting to setup Failover Clustering using two VMs from within a Vcenter. Each virtual machine resides on a seperate physical host following this schema:


The instructions for adding a disk to the first machine go as follows:

  1. In the vSphere Client inventory, select the newly created virtual machine and select Edit Settings. The Virtual Machine Properties dialog box appears.
  2. Click Add, select Hard Disk, and click Next.
  3. Select Raw Device Mappings and click Next.
  4. Select an unformatted LUN and click Next.
  5. Select a datastore and click Next.

This datastore must be on a SAN because you need a single shared RDM file for each shared LUN on the SAN.

My question is as follows. When two Windows 2008R2 servers are hosted on two different physical VMWare servers within a VCenter, is it absolutely necessary to have an unformatted LUN for the shared storage of a Windows Failover Cluster?

If not, what would be an alternative?

iSCSI is not an option. Both servers must be installed on two seperate physical hosts.

Here is a link to the documentation.


Goto page 21.

  • I am not sure if you are asking whether you should have shared storage, or whether you should specifically have an "unformatted LUN". Could you please clarify? – RoKa Apr 10 '13 at 9:33
  • Its shared storage using an unformatted SAN LUN with RDM as opposed to VMFS in VMWare. – Craig Efrein Apr 10 '13 at 9:38
  • I can (almost) conclusively say that in your scenario, you will definitely need a LUN and not VMFS to cluster SQL. – RoKa Apr 10 '13 at 9:41
  • RoKa, please put your comment in an answer and I will check it off. Turns out I definitely needed to use three independant LUNS in RAW after all. All of the vmware documentation makes that requirement quite clear. – Craig Efrein Apr 11 '13 at 9:28

As said in the comments, I can (almost) conclusively confirm that you will require shared raw LUNs with RDM, when you want to cluster 2 x virtual (vmware) SQL Server nodes that are on different hosts, instead of using VMFS.

The VMWare documentation also explicitly mentions the use of unformatted LUNs

*I guess (and I have never done touched on it before) the only possible exception that spring to mind may be in you use SQL Server 2012 AlwaysOn on SSDs. Oh, and possibly iSCSI, which is as you said, not an option. *

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