Vmware ESXI 3.5 and Quad core CPU

[Lukas_R]

Hello,

we have server from IBM with 2x Quad core Intel CPU.

I try free version of Vmware ESXI 3.5, but quest OS (OS installed on top of VmWare) sees only 4 CPUs. Do I need to purchase any additional license to use 2x Quad core CPUs? Because Vmware ESXI 3.5 should support up to 2 physical CPUsf for free?

VmWare infrastructure client in the configuration tab says that our system has 2 physical CPUs and 8 Logical CPUs..

thx

Lukas

[weinstein5 · Accepted solution]

Welcome to the Forums - The 2 CPUs represent the two physical CPUs in your host - the 8 logical CPUS are the 8 cores in the 2 physical CPUs in your Host - now in regards to the virtual CPUs in the VM you are seeing the limit to number of virtual CPUs you can have in a virtual machine - with ESXi/ESX your virtual machines can only have 1,2 or 4 virtual CPUs - so there is no way for your VM to see more than 4 VMs - Also to give you best practice in regard to virtual SMP start off with a single vCPU and only add additional vCPUs if needed -

If you find this or any other answer useful please consider awarding points by marking the answer correct or helpful

[Lukas_R]

Thx fo so quick answer.

So, I can say that for the server with 2x Quad core CPUs this Vmware version is not good? and should not be used?

And here is no additional license to add more CPUs?

It is strange, because it is good for server with 2x Dual core CPUs, which is physical the same..

What you can suggest for our server?

thx

Lukas

[weinstein5]

The dual Quad Core box actually is a nice box and well suited for ESXi - you should easily be able to support 25-30 VMs easily - if not more. This of course assumes you have enough memory/network and disk resources - the free ESXi version supports up to 32 cores per physical host - when you register your ESXi software you specify the number of physical CPUs you want to support - so there really are no additional cost to support additional CPUs -

Now in regards to the virtual SMP - vms with multiple virtual CPUs - the best practice I talked about comes about form how the ESX host schedules the virtual CPUs - it schedule the vCPUs simultaneously so it can not all vCPUs at the same time it will schedule none of them thus impacting performance - by starting off with a single vCPU eliminates this form occurring and making it easier for the CPU to be scheduled -

If you find this or any other answer useful please consider awarding points by marking the answer helpful or correct

[Lukas_R]

But, if I need only one VM right now it can NOT use all CPU power of my server, because it supports only 4 CPUs per VM..?

So, for such situation I should use other VmWare product? Or use minimum 2 VM on Vmware ESXI 3.5 to gan full possible power of my CPUs? Or I am wrong?

thx

Lukas

[weinstein5]

Yes that is correct a single VM would only be able to use 4 out of the 8 cores in your host - I think you are not understanding the benefit of virtualization - first step is understand why you would want to virtualize - hardware as been following Moore's Law - that computing power doubles approximately every 2 years and this has held for more than 40 years - in the x86 world this means that the hardware is more powerful than the applications that are running so the systems sit idle the majority of the time which means datacenters and servers around the world have equipment that is barely utilized (on average less than 6% - 8%) - what virtualization allows you to do is run multiple vms on the single piece of hardware - so by placing multiple VMs on your ESX hosts will in sure that not only the the CPUs but also memory, netowrk and disk bandwidth will effectively utilized through out the day - so now looking at your situation I do not know what applications the physical servers are running but I will bet if you look at their utilization by and large will be nominal maybe peaking at a point or two during the day probably average 6%-8% throught the day - so you will be able to run multiple VMs on the host and that means more than 2 - however if the server is being heavily utilized throught out the day at a constant 60%+ per physical CPU in the machine it is probably not a good virtualization candidate -

ESX/ESXi are the VMware products designed for the datacenter and will provide the best performance so I would not look at any other products if you are looking for the best performance -

[Lukas_R]

Hello,

thx a lot for so detailed answer.

One more thing, what is main differences between ESX and ESXi? I found what it is only "32 MB disk footprint" in ESXi, is it all? And how it can effect our system?

thx

Lukas

[weinstein5]

The virtualization engine, called the vmkernel, at the heart of both is the same - the major difference is ESX has something called the service console which is a specialized RHEL VM that allows you to interact with the vmkernel - ESXi does not have this but can be added using a virtual appliance called the Remote CLI - without the Service COnsole you get an improved level of security - ESXi is the direction that VMware is heading -

[jhigham]

David,

I also have a 2X 4 core setup running ESXi with several VM's running. One VM is a CentOS 5.2 install with cPanel WebHost Manager running. It (CentOS) was created with 2 virtual CPU's.

Question: Can I shutdown the VM and increase the CPU count to 4? What is the impact of switching (increasing or decreasing) virtual CPU's with CentOS/RHEL?

Thanks

[weinstein5]

Yes you can shutdown the VM and add 2 more vCPUs - in terms of the impact it depnds on many things - if the applicaiton is ,ulti threaded and will take advantage of the extra processors in terms of the Virtual environment will depend on what other VMs are running and how many vCPUs they have -

If you find this or any other answer useful please consider awarding points by marking the answer correct or helpful