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VMWare ESX – Virtual Sockets vs Cores per Socket

We recently updated our VMWare ESX servers to ESX 5.0 which introduced some new features. One of the features is that you can choose between Virtual Sockets and Cores per Socket. I was wondering what the performance difference was between the two. I found an interesting discussion on the SpiceWorks community that confirms my thoughts.

When you select Virtual Socket, the core will be presented to the VM's OS as an actual hardware socket. If the application has been optimized for multiple sockets specifically, it will benefit from this. Same goes for selecting multiple Cores. I can't find any information on what it does to the host's performance though, but it has been mentioned that there's no performance change between the two options. The feature was also introduced for software licensing that is socket or cores based.

Microsoft has already announced that many of the new versions will be on a per core license model.


Event 58 – The disk signature of disk n is equal to the disk signature of disk n

Log Name: System
Source: partmgr
Event ID: 58
Task Category: None
Level: Warning
The disk signature of disk 2 is equal to the disk signature of disk 0.

This error occurred on one of the virtual machines on the ESX environment. It probably also caused another error a bit further up in the event viewer.

Log Name: System
Source: VDS Basic Provider
Event ID: 1
Task Category: None
Level: Error
Unexpected failure. Error code: D@01010004

Disk 0 is the system disk, which contains the Windows 2008 R2 installation. Disk 2 on the other hand is non-existent, or better said, hidden. This error can easily cause errors with your backup software like Backup Exec.

You can also run into this error when you're using Hyper-V and you're making a backup using Backup Exec by means of the Hyper-V agent. It will then mount the virtual machine disk on the host server. If the host server disk and the virtual machine disk have the same disk ID they will clash causing event id 58.

If you do the following, you can get the current disk ID:

  1. Start a cmd as administrator
  2. Type:
  3. Type:
    list disk
  4. Type:
    select disk 0

    (replace the 0 with the disk indicated in Event ID 58)

  5. Type:
    detail disk

As you can see, my disk ID is 3B9ED7B7. This seems to clash with another hidden disk that has the same disk ID. To change the disk ID you'll have to download the Windows 2000 resource kit or if you can find it with Google dumpcfg.exe or dumpcfgx64.exe if you're on 64-bit.

Once you've downloaded the utility you'll have to start a cmd as administrator, and run the utility with the parameters -S followed directly with the new disk ID, a space and the number of the disk that you used in the select disk command above.

  1. Start a cmd as administrator
  2. Type:
    dumpcfgx64.exe -S3B9ED7B8 0
  3. Or use diskpart and select disk (ID) then type:
    uniqueid disk id=3B9ED7B8

When you follow the procedure to get your disk ID again you'll notice that it's been changed to the new value.