I recently updated my SCVMM server to Update Release 6.  However once updated, I was getting error 21201  “Another machine with the same SMBIOS GUID is found. Recommended Action An SMBIOS GUID should uniquely identify the machine. Provide the correct value or contact the machine manufacturer to help update the hardware with correct information” as pictured below:

In my case, I think this was because I had removed a host from the cluster and then re-added it.

The fix was as follows:

Go to SQL Server Management Studio and connect to the VirtualManagerDB.  Then run the following query:

This should return a number of rows equal to the number of hosts in your environment.  Mine returned the following:

Next execute the query:

In my case, this returned one more row than the number of hosts I had in the environment.

I exported this information to Excel (right click the grid and Save as) and matched them up getting the following:

You can see that the green and black rows match on SmBiosGuid.  By looking at the PhysicalMachineId I could see which was the redundant record (black).  Therefore I deleted this row from the PMM_PhysicalMachine table.  I did this by going to the table and choosing to edit top 200 rows (as pictured):

Then (once I had a full DB backup) I just right clicked the row I wanted to delete and deleted it.  This fixed the issue and SCVMM can now refresh the host successfully.