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Omniman
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Upgrading a VM Host CPU Question

Thu Sep 14, 2017 7:55 am

I wasn't sure which section of the forum to actually post this in so please forgive me! I've never swapped a CPU on a VM host before and I'm curious if it will make the guest OS's freak out and possibly make them want to reactivate against Microsoft? I'm running VMWare's vSphere Hypervisor 6.5a on my Lenovo Thinkserver home test lab box. The Xeon it came with is basically the lowest of the low that the motherboard supports so it's a quad core without HT. It was a great price at the time about 5 or 6 years ago and I figured I'd buy a used higher end supported Xeon on eBay now that I'm starting to see the median host CPU utilization is starting to really get brutalized with noticeable performance issues on the guests. Thanks!
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Re: Upgrading a VM Host CPU Question

Thu Sep 14, 2017 8:04 am

I've never had a problem with Windows activation when changing host hardware, provided I don't change the configuration of the VM itself.

Disclaimer: This has been with VirtualBox instead of VMware, and I haven't tried it (yet) with Windows 10.
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techguy
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Re: Upgrading a VM Host CPU Question

Thu Sep 14, 2017 8:06 am

I am by no means a VMWare expert, but my understanding of the matter leads me to believe that the CPU is presented by the Hypervisor to the guest OS as a rather generic virtual CPU, which should prevent the scenario you raised in your question. MS determine Windows activation based on a hardware stamp that is created at install time, and which is primarily determined by the motherboard in use (according to my understanding). I don't know if any of the motherboard resources are presented via the Hypervisor or if a generic representation is presented to each guest OS through the Hypervisor's VM template. I'm sure someone with more specific knowledge will come along to correct me if I'm wrong.
 
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Re: Upgrading a VM Host CPU Question

Thu Sep 14, 2017 8:07 am

I think this should be fine, particularly as you're sticking with the same motherboard. I've done this on other hypervisors (Xen, QEMU/KVM, VirtualBox) and been fine, including a full platform upgrade (motherboard, CPU from Intel to AMD, RAM) on a QEMU/KVM dev box, though on that occasion a couple of minutes tinkering was required IIRC.

Logically, this is the same thing as migrating the VMs -- so long as the hypervisor is the same one, it shouldn't be painful (based on my experiences, anyway).

I don't know about licence activation though, my Windows VMs were all activated with KMS.
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TheRazorsEdge
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Re: Upgrading a VM Host CPU Question

Thu Sep 14, 2017 8:46 am

Omniman wrote:
I wasn't sure which section of the forum to actually post this in so please forgive me! I've never swapped a CPU on a VM host before and I'm curious if it will make the guest OS's freak out and possibly make them want to reactivate against Microsoft? I'm running VMWare's vSphere Hypervisor 6.5a on my Lenovo Thinkserver home test lab box.


No, a CPU change alone is not sufficient to trigger reactivation.

That said, if you've deleted/replaced NICs somewhat recently (or made other virtual hardware changes), the CPU change may push you over the edge.
 
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Re: Upgrading a VM Host CPU Question

Thu Sep 14, 2017 8:53 am

techguy wrote:
I am by no means a VMWare expert, but my understanding of the matter leads me to believe that the CPU is presented by the Hypervisor to the guest OS as a rather generic virtual CPU, which should prevent the scenario you raised in your question.


This is incorrect. The guest OS should see the correct CPU, including its model and family/stepping/PHY info.

I don't know if any of the motherboard resources are presented via the Hypervisor or if a generic representation is presented to each guest OS through the Hypervisor's VM template.


VMware presents a universal VMware-branded motherboard.

In fact, for Windows machines, the easiest way to target GPOs to VMs is to configure a WMI filter based on the motherboard manufacturer.

Microsoft does the same thing with Hyper-V. At least, this was the case with their first generation VMs---no experience with the latest, but I assume it remains similar.
 
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Re: Upgrading a VM Host CPU Question

Thu Sep 14, 2017 9:46 am

I think the only time might end up with a freak out situation (with regards to the OS, not necessarily activation) is if you migrated the VM from an Intel-based host to an AMD-based one. Since you're just upgrading the CPU in the same host, you should be fine on all fronts. Hyper-V does pass the actual CPU through to the guest OS, and as far as I know, VMware does, too. In fact, with Windows Server 2016's Hyper-V (and the current Windows 10 release) it even passes the CPU's virtualization features to the guest OS so you can enable Hyper-V in the guest. I'm not entirely sure what the point of running a VM in a VM would be, but the capability is there. It probably has something to do with future plans around containers and such.

With regards to purchasing an upgrade CPU for an older box, take a look at StarMicro, Inc. They carry CPU pulls and have the older ones fairly cheap. They off a 30-day money back guarantee and a one-year replacement warranty.



TheRazorsEdge wrote:
In fact, for Windows machines, the easiest way to target GPOs to VMs is to configure a WMI filter based on the motherboard manufacturer.

That's....not exactly how I would do it, but then there are so many ways to target GPO's using WMI and/or Security Filtering. Hyper-V VM's will actually have a computer system model of Virtual Machine. I would think VMware VM's would, too, but I have no way to verify.


TheRazorsEdge wrote:
Microsoft does the same thing with Hyper-V. At least, this was the case with their first generation VMs---no experience with the latest, but I assume it remains similar.

It's still the same.
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Omniman
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Re: Upgrading a VM Host CPU Question

Thu Sep 14, 2017 10:16 am

Well thank you everyone! I feel better about it now and some very interesting information as well!
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