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racket
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ESXi 5 VM cpu limits question

I have a host running ESXi 5. Nothing fancy, just a dual proc 6-core system with hyperthreading, totaling 12-cores @2.66ghz for about 31.92ghz total capacity.

The best solution for what I need would be to would be to wipe it and install my os on it, but that can't happen currently. For sizing purposes I essentially need the entire box. I can only create a vm that is allowed 8vcpu @2.66ghz. This creates a reservation cap of ~21.28ghz. Does this mean that I would be wasting ~30% of my box. If I saturated the vm, I would never see above utilization of about 22ghz + hypervisor utilzation? If so, any ways around this besides scaling out horizontally?

I guess another way of asking this would be, if I created a 2-vcpu vm on the host without setting any reservations or limits, could it ever use all of the systems available cpu capacity or is it just limited to whatever 2-vcpu is?

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GMCON
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I will just respond to your last sentence as that seems to make more sense.  If you only assign 2vCPU to a VM it will never scale above that 2 CPU it is a hard limit. Even if you have the "Unlimited" check box checked it does not mean it will scale to use all the CPU's if it needs to, it will still only use 2vCPU's worth of resources.  All the unlimited check box means is that the VM can use all the resources assigned to it.

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a_p_
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Welcome to the Community

with the limitation of 8 vCPUs you mentioned, I assume you are using the free Hypervisor edition. All other (paid) editions do not have this restriction (see VMware KB: Licensing for vSphere 5.5 ). With 8 vCPUs assigned to the VM, the host will schedule 8 vCPUs (cores, incl. HyperThreading) at a time to the VM, i.e. the other cores will be mostly idle with only this single VM running.

André

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weinstein5
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What application will you be running on the VM because my experience is very few applications need more than 2 vCPUs -

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GMCON
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I will just respond to your last sentence as that seems to make more sense.  If you only assign 2vCPU to a VM it will never scale above that 2 CPU it is a hard limit. Even if you have the "Unlimited" check box checked it does not mean it will scale to use all the CPU's if it needs to, it will still only use 2vCPU's worth of resources.  All the unlimited check box means is that the VM can use all the resources assigned to it.

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King_Robert
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see the below detailed configuration limit for ESXi 5.1 VM

Virtual Machine Configuration Limits

Virtual CPUs per Virtual Machine32 vCPUs
RAM per Virtual Machine1,024 GB
Virtual Disks per Virtual Machine 62
Virtual Disk Size 2000 GB
Virtual NICs per Virtual Machine 10
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