Citrix advertises XenServer as supporting 8 VCPUs per guest Windows VM, but doesn't offer any method for actually achieving this on Windows operating systems that are limited to 4 physical sockets.

Another thread ([m-1375191]) suggests the command:

xe vm-param-set platform:cores-per-socket=4 uuid=xxxx

But XenServer 5 update 3 doesn't seem to respond. There is no documentation with regards to what keys are available for the platform: command.

Can anybody help me to use all 8 cores on a 2x Quad Core Xeon server under Windows 2003? Without this, XenServer has no advantage to me over VMware ESXi.

Well, it is the same here with XenServer 5.0 Update 3 on a very plain machine with AMD Phenom. Windows 2003 Server (Standard Edition) can use only 2 CPUs (Std. Edition works only with 2 sockets). The "secret" parameter for VM and / or template does not do anything.

My guess is, that it has something to do with the licensing of XenServer. The free license sets the number of supported sockets to 0... Mabye the "hack" which takes care about the setting of the cores-per-socket-value has a bug and falls back to one core = one socket...

Fix would be good (even if it occurs only on "free" license),...

Samuel

Are you running this command on a server installed with Free XenServer, or one with a "Citrix Essentials for XenServer Enterprise Edition" license? If the former, can you install a 30-day trial license for Citrix Essentials for XenServer, Enterprise Edition and re-try?

-Bill

So there is still no additional proof available why the cores-per-socket parameter seem to work on some machines but does not do its job on others?

As long as it is not sorted out, that the problems occurs only on a free XenServer version, I doubt that most of potential customers want to use it in any production environment. It would mean that they are obliged to upgrade their Windows Server licences...

In either way, it should be announced as a know issue, that free XenServer supports only 2 cores per Windows Server standard licence....??

Thomas

Windows XP Home edition supports up to 1 processor or physical socket
Windows XP Enterprise or Professional Edition supports up to 2 processors or physical sockets.

The amount of cores on a physical server per processor is not important.
It is however on a virtual platform. Normally a vCPU equals 1 core and is presented to a the VM as a single processor without any cores.

*With the XenServer Enteprise Edition license* you can actually unlock a hidden feature which is the capability to present a processors with a certain amount of cores.
So if have a 2 socket quad core server, and a XenServer Enterprise Edition (or Essentials for XenServer Enterprise Edition) license you can actually present 2 processors to a Windows XP VM, with each processor 4 cores.

Peter

so using command:

"xe vm-param-set platform:cores-per-socket=4 uuid=xxxx"

on XenServer free version will not work for sure? I've just tried this command on XenServer 5.5 and Windows 2008 x64 and nothing has changes. I'm still having number of CPUs in VM = number of vCPUs assigned to VM.

Indeed the cores-per-socket feature is only available on the Enterprise and Platinum editions.

Peter

I have need to use this command and I do have enterprise edition. The purpose is one of our applications is licensed by cores and not sockets.
We have XS 5 update3 with dual AMD quad core as hosts, and the windows 2008 VM shows quad core.
I need the windows VM to see only ONE core.
I see the command posted in this thread, but where do i get numbers to fill for xxx, and also this VM is part of XS Farm with XenMotion, All hosts in farm are identical, will i need to adjust or apply command in special way?
thx

The uuid=xxx stands for the unique identifier that each object has in the XenServer database.
In this case a Virtual Machine object.

So for your VM you want to do:
xe vm-list name-label="VM Name as displayed in XenCenter"
This will display the UUID for that VM.

Note that you also use wildcard approaches to apply this too multiple/many VMs.
As well as templates.

Peter,

The Citrix XenServer free it´s not Enterprise Edition? Where I get this?
I dont net Essentials. Just a cores-per-socket function.

Thanks

The freeware version offers a lot, but obviously not everything. Citrix needs to make some money on the product in order to give away as much as they do. For a comparison of what the Essentials version offers vs. the free version, see: http://www.citrix.com/English/ps2/products/subfeature.asp?contentID=1680964 for details. Educational institutions can also get pretty good discounts.

Might want to be more specific...this comparison says nothing about vCPU's or other 'limitations' int he Free version, other than HA and similar features lacking. I have a case open with Citrix to get the definitive documentation and will report back if/when I get it. It's not a show-stopper, but it sure is a pain to find out after the fact that there are Free limitations that no one knows about...

PS: not to mention that Essentials does even appear to be an option at all anymore.

Edited by: Brett Walters on Aug 26, 2010 12:35 PM

>Can anybody help me to use all 8 cores on a 2x Quad Core Xeon server under
>Windows 2003? Without this, XenServer has no advantage to me over VMware ESXi.
I think it's a waist with 2003 but whatever

To get 2 vCPU with 4 cores each do the following,

shut down the VM, then on the XS CLI:

xe vm-list (to get the vm-uuid)
xe vm-param-set platform:cores-per-socket=4 uuid=<vm-uuid>
xe vm-param-set VCPUs-max=8 VCPUs-at-startup=2 uuid=<vm-uuid>

start the VM in question.

Thomas
--
http://www.ThomasKoetzing.de

For completeness, the multiple cores per socket feature is only available in the premium (paid for editions).
And NOT in the free edition.

Which means available in the Advanced, Enterprise and Platinium Editions.

Peter

Understood, from all the posts on the subject...however - where is this stated in any of the documentation or edition comparisons?

Is there a way to set this per host or per Pool? it seems like this should not be a VM-specific parameter since this relates to the underlying hardware, not a VM.

Is there a way to set this per host or per Pool? it seems like this should not be a VM-specific parameter since this relates to the underlying hardware, not a VM.

(sorry for the double-post, please delete if possible)

Edited by: Tim Fournet on Oct 15, 2010 11:19 AM

Hello-
Just to avoid being a worthless lurker i figured i'd respond with my findings on XS6.0

First off, I have a dell m1000e chassis with 5x m610 blades, each with dual xeon 1.86ghz quad-cores and 24G mem. I too tried applying the cores-per-socket on the free version to a particular VM which was Windows XP SP3 32 bit. Nothing doing.

So as a proof of concept, i got the trial version of the advanced (read: cheapest) version of the for-pay Xen. Now it works. Amazing.

One catch - make sure NONE of the blades in your pool are still the free version, or it won't work. That one took me a minute to figure out. I guess because they all have shared iscsi storage and xen motion could possibly move them to a free-versioned blade, it wouldn't allow the 8 vcpus until all 5 blades were advanced.

I had been combing the threads and never saw a definitive statement about the free - vs - pay situation, only conjecture. CASE CLOSED.

I have the Advanced license for Xenserver and after setting the following parameters, I still cannot get Windows to recognize more than 1 core per socket. I am using Windows Server 2008 R2. I have set the following parameters based on this KB article: http://support.citrix.com/article/CTX126524

xe vm-param-set platform:cores-per-socket=4 uuid=
xe vm-param-set VCPUs-at-startup=8 uuid=
xe vm-param-set VCPUs-max=8 uuid=

Task Manager now shows 8 cores; however, device manager is showing 8 CPUs as well. I was under the impression that using these parameters device manager would only show 2 CPUs.

Any assistance would be appreciated. Thank you.

Same behaviour here:

Tested with 2008R2 SP1 VM on HP BL460c G7 Blade Server with 2 Xeon E5640 2.67Ghz, XenServer 5.6 is showing 16 CPUs

After applying the XenServer Enterprise License to all my servers within the pool, i was able to do some testing

first tested:

xe vm-param-set platform:cores-per-socket=4 uuid=
xe vm-param-set VCPUs-at-startup=8 uuid=
xe vm-param-set VCPUs-max=8 uuid=

This shows me 8 Cores within the Task Manager and 8 Processors within device manager

second tested, the way thomas mentioned a few posts ago:

---------------------------------------------------------------------
I think it's a waist with 2003 but whatever

To get 2 vCPU with 4 cores each do the following,

shut down the VM, then on the XS CLI:

xe vm-list (to get the vm-uuid)
xe vm-param-set platform:cores-per-socket=4 uuid=<vm-uuid>
xe vm-param-set VCPUs-max=8 VCPUs-at-startup=2 uuid=<vm-uuid>
---------------------------------------------------------------------

The VM still shows 8 cores within Task Manager and device manager

Additionally I found out the following strange behaviour:

- I have got an HP BL460c G7 Blade Server with 2 Xeon E5640 2.67Ghz
- XenServer shows me 16 available CPUs
- Tried to give all 16 CPU´s to one VM with the following Commands

xe vm-param-set platform:cores-per-socket=8 uuid=
xe vm-param-set VCPUs-at-startup=16 uuid=
xe vm-param-set VCPUs-max=16 uuid=

- After starting the VM it hangs while booting windows
- Also all configurations where the value of "cores-per-socket" is higher than 4 the VM hangs while booting windows.
- Am I doing something wrong or have I missed something???

Thanks for your help