Hi,
I have 2xQuad core Intel 5410 Xeon CPU server. Everything looks normal on ESXi server interface. The system found dual quad core CPU. It shows 8 CPU which is correct.
But, when i want to create a new virtual machine, I can set 1/2/4 CPU. There is not an option for 8 CPU. Is that normal?
License issued for 2 CPU, this is correct too. Because phisically 2 CPU, and 2CPUs are quad cores.
Are there any users having the same issue?
Thanks
That is normal since vSMP only supports up to 4 CPUs per VM. In general, you should only use more than 1 vCPU if you run Software that really takes advantage of it and uses the vCPUs. Otherwise it will result in an unessecary moving from vCPUs across the physical CPU to load balance them, which costs ressources, too.
Kind Regards,
Gerrit Lehr
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Welcome to the forums - 4 vcpus is the maximum number of cpus you can assign to a virtual machine - so this is normal behavior -
Why do you need a quad vCPU VM? - best practice is to start with a single vCPU and more if needed -
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Welcome to the forums,
The behaviour you are seeing is expected, currently a VM Guest can be configured with a maximum of 4vCPU's. see these doc's for details about VM Guest Maximums
further is is not considered best practice to configure a Guest with more than a single vCPU unless performance is shown to need it. you start at 1 and work up towards 4. the reasoning behind this is because the vCPU map directly to a pCPU or pCore a Guest will need the total number of pCPU or pCore available each instruction. this can reduce the efficiency of Guests in certain circumstances. have a view of the below mentioned doc.
Powerpoint presentation on scheduling
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Tom Howarth
VMware Communities User Moderator
Thank you for the answers. I appreciate. It's clear now. There are limits that I have to use on per virtual machine.
But, Let's say I created 4 virtual machine and each VM has configured with 4CPU with the max. So, will all VMs use same CPU which has 4 core, or will all CPU requests be balanced to 2 physical -8 core- CPU? How can I understand that all hardware resources are being utilized?
I think, It's designed per CPU as 2 logical CPU by vmware, that's why I can configure 4CPU per virtual machine when I have 2 physical CPU? So I will not be worried if both CPUs are being utilized or not
Configuring 4 4vCPU guests on a machine with only 8 cores is a recepie for disaster. Co Shecduling has greatly improved but you will possilby see a high CPU ready value where threads on your guest machines are waiting for a free host core to execute an instruction on.
If you configure 8 Single vcpu machines and run something CPU intensive on them , you'll see some CPU utilisation.
What are you planning to run on these VMs?
Regards
Leafy911
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The vmkernel will utilize all cores and will balance the vmw load across all cores - the issue of what you want to do is due to the scheduling of the vcpus as chris indicated - the vmkernel will sc hedule the 4 vcpus simultaneously and if there is not enough processor cycle vailable for any single vcpu all 4 will NOT get scheduled - thus impacting the performance of the vm - that is why, unless you are sure the vm needs it, start with a single vcpu -
Hi Guys,
I appreciate for the answers. I am trying to understand. So, I will have 4-5 vms on it. All vms will have different hosting panels. cpanel/DA/plesk/dotnetpanel will be used on each vmware. All vms will work as db/web/mail/dns server.
What is your suggestion for CPU configuration on each VM? Should I use 2 CPU on each machine or 4 would be a problem?
Additionally, based on your experience, would it be better to have some free RAM/HDD on the ESXi server, in order vmware to perform better?
No as per our earlier advice, you start at a single vCPU for your guests, as this make CPU schduling easier. Best Practice is to use a single vCPU. you use vSMP sparingly.
Tom Howarth
VMware Communities User Moderator