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Nirvaanaa
5 pts.
 Allocating 2 CPU for a VM
VMware ESXI 4.0 Performance, Virtual Machines, CPU, CPU Utilization, vSphere
Hi there,

Iam vmware conultant for a coporate organisation, i would like to know what are the disadvatanges of adding 2 CPU on 1 VM for 2 node VM cluster example, cluster has 10 VMs and i add 2 CPU to one or two VM will this make the cluster inconsistent. 

I can see increase in performance of those VM.. not sure if this will affect overall cluster perfomance.


thank you for thie facility...


regards

shravan


Software/Hardware used:
AMD-Vsphere
ASKED: May 18, 2011  7:05 AM GMT
UPDATED: May 22, 2011  7:08:08 AM GMT
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Mrdenny
63,630 pts.
Answer Wiki:
It all depends on what the rest of the VMs are doing and how many cores the physical server has. If you have 8 total cores and 10 VMs, and all the VMs are pretty busy already you won't get much benefit from making the VMs dual vCPU. Sorry but there's no really hard and fast answer to this.
Last Wiki Answer Submitted:  May 22, 2011  7:08 AM (GMT)  by  Mrdenny   63,630 pts.
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Hi Shravan,

You can easily do this, however best practice is to only add 1 vCPU to a machine if it is possible. One of the biggest considerations here is how many cores do the physical servers have per processor. Keep in mind, 1 vCPU is equal to 1 core, not physical CPU (unless they are single core processors).

The downside to adding more is that there may be increased wait times for the VMs to access the physical CPUs in order to do their processing. However, in your example of 10 VMs across 2 physical servers and each of those servers have 2 quad-core processors then you effectively have 16 vCPU’s to work with and you should be easily able to assign 2 vCPUs to that server. However if the number of VMs grow noticeably (and it likely will) then you will start to have more CPU contention as the machines have to wait longer periods.

Matt

Mattcassell
 705 pts.
 

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