The vmx-10 Paradox

vmx-10 paradox



Since the introduction of vmx-10 there has been a lot of debate on whether to use it or not.
The  main shortcoming is that one cannot edit the settings of a Virtual Machine that is running on VM hardware version 10 (vmx-10) using the vSphere client.
It can only be done using the web client, so if you are running just an ESXi server and you have a VM with vmx-10, you are in trouble.


Also, I realized that even when you have a vCenter server, if its installed on a VM that is running with vmx-10 you will still get into trouble.
It could all start with something simple, like the vCenter going down because the  C:\ drive is full and thus the service does not start. Which is exactly what happened in my case!


Now the vCenter is down, and I need to add space to the C drive, by editing it,  but the vCenter is down and so is the web client.
I could login into the ESXi host that is hosting the vCenter server to make any changes, but again I would need the web client. This brings us back to square one.


I racked my brains for a while about this and then thought of trying this, using the vmkfstools.
So I logged into my host and powered off my vCenter server ( the service was not running anyway), located the server under /vmfs/volumes///

Warning : Do not extend a disk that has snapshots. Commit or discard snapshots before increasing the size of the virtual disk. Extending the size of a virtual disk that has snapshots invalidates the snapshots.

The command that came in handy to extend the disk space was

vmkfstools -X 60G /vmfs/volumes/datastore/vcenter-server/vcenter-server.vmdk

This extended  the disk and gave some space to the C drive, so it could do what it does and get the vCenter service up and running.

This got me thinking, what if the same thing happens because of other resources like RAM and CPU?

That is when I stumbled upon a KB Article that tells you how to make these changes using PowerCLI commands when you don’t have a web client in your environment or when its down.


To conclude :

If you do not have a need to run your vCenter server on vmx-10 then avoid it until VMware changes the architecture and the way the machine settings are edited in higher versions of VM hardware. If you need to run the vCenter VM with vmx-10 then keep the KB Article handy as it will help you perform these operations on the VM directly using powercli cmdlets.


Take a backup of the vCenter server before you do any of these tasks.

UPDATE : With the release of 5.5U2, you can edit VMX-10 using C# clients. VMware finally realized it.



  1. Rehman Memon

    Hi! Can you please post the link to the KB aricle?

    • admin

      KB Article for?

  2. Koray

    How did you manage to increase the partition size after increasing the disk size to 60G?

  3. Abhilash HB

    Hi Koray,
    I powered the machine back on, re-scanned for free space and extended the partition.

    • Koray

      Oh of course.. You cannot edit VM settings but you can open console via a client connection to ESXi. Good hint, thx

      • Abhilash HB

        Since it’s a windows box you can just RDP into it and extend it after its up.

  4. virtblackbelt

    I’m confused why you didn’t just log into the vCenter VM directly and clean up the disk before going through all the gyrations of using vmkfstools.

    • Abhilash HB

      We tried cleaning up the disk but we did not find any space that could be reclaimed. The whole problem started because the vCenter machines were given less space to start with. Now we have increased our standard size to a bigger drive for vCenter servers.

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