Suddenly my CPU cannot support 64-bit guest hosts?

[kjrehberg]

I haven't encountered this until I upgraded to VMware VSphere.  I can use VirtualBox and other hypervisors on this machine to support 64-bit guest hosts, but for reasons I cannot understand, VMware VSphere refuses to support 64-bit guest hosts on this machine.

The machine is a rather recent vintage Dell PowerEdge SC440 with an Intel Core 2 Duo E4500 CPU.

When I used a regular operating system on this host, it certainly supported 64-bit host and guest operating systems.  When I installed VSphere on this machine, it only supports 32-bit guest operating systems.

What is wrong with this?  There is no practical reason this machine cannot support 64-bit guest hosts except for VMware VSphere's limitations.

I welcome any comments and suggestions.  I can certainly upgrade the CPU, but since I've used 64-bit guest hosts on this machine without VSphere, I am apt to decline that suggestion.

Thanks!

[sumitpatel]

Hi,

You should check your BIOS of Dell Server. There shold be one option called " VT Technology" or "Virtualization ".

Also check " 64-bit Support"  attribute and if it is disabled, Enable it , save changes and  Restart your Dell Server and then try to install 64 bit Guest OS . It should work.

Let me know if this helps !

Regards,

Sumit

[Rumple]

You will most likely need to power down server and then power it back up for changes recommended by sumitpatel to take effect.

I typically pull power cords just for good measure just to be sure.

[admin]

The E4500 does not support VT-x.  While this system can run 64-bit *host* operating systems, it cannot run 64-bit *guest* operating systems under any VMware product.  See http://kb.vmware.com/kb/1003945 for more information.

[kjrehberg]

Okay, so, why does VirtualBox support 64-bit guest hosts on this system?

[admin]

On systems without VT-x, I believe that VirtualBox falls back to emulation through qemu rather than virtualization. Do your guests under VirtualBox run pretty slowly?

[kjrehberg]

I haven't noticed any performance difference but I don't have a real 64-bit VT-x system to compare it with.  I do know that "vmx" does not appear in /proc/cpuinfo on the guest nor on the host.

[admin]

Try running a 64-bit guest under VirtualBox, and see what top reports on the host.  I would guess that qemu will be at the top of the list.

Note that the VirtualBox manual (https://www.virtualbox.org/manual/ch03.html#intro-64bitguests) says that hardware-assisted virtualization is required for 64-bit guests.  However, I believe this is incorrect.  At one time, I accidentally installed a 64-bit guest under VirtualBox running in a VM without virtualized hardware-assisted virtualization, and the installation was successful.  It just took about 10 times as long as normal.

In any event, you need hardware-assisted virtualization support to run 64-bit guests under VMware products on Intel hardware.