When you attach a GPT pass-through disk provided from SAS storage (Serial attached SCSI) array to a highly available virtual machine by using the Hyper-V Manager or Failover Cluster Management Microsoft Management Console (MMC) snap-in, the System Center Virtual Machine Manager 2008 Admin Console lists the status of the virtual machine as "Unsupported Cluster Configuration."
Details on the High Availability section of the VMs Properties in SCVMM are:
Highly available virtual machine <Machinename> is not supported by VMM because the VM uses non-clustered storage. Ensure that all of the files and pass-through disks belonging to the VM reside on highly available storage.
GPT pass-through disk provided from SAS storage array is not supported in System Center Virtual Machine Manager 2008 R2.
This limitation only applies if the pass through disk provided from a SAS storage array in a clustered environment is GPT. There are two workarounds for this: 1. Add the LUN from the SAS storage to the cluster, create a CSV and place the VHDs on it and attach those to the VM. 2. Create MBR pass through disks and attach those to the VM. Note that both VHD and MBR pass through disks are limited to 2TB in size.