How-to determine the number of vCPU’s to allocate to virtual machines

How many vCPU’s to allocate to virtual machines?

When creating new VM, one of the first questions is “how many vCPU’s to allocate to virtual machine”…. When you start an assistant in VMware vSphere and start to create a new VM, it will pick up the “right” elements depending on the template which you’ll choose from the drop down box. The correct hdd controler, network card type, etc etc… But the values about the vCPU are the not always the best to fit your environment.

In the new whitepaper created by David Davis and Alex Rosemblat called vCPU Sizing Considerations, you’ll learn more about the process, when and how to correctly pick the number of vCPU for your VM.

In addition, when creating Win 2003 VMs, there might be another thing to consider – the HAL (The Hardware Abstraction layer). It’s because when changing the vCPU in Win2003, the HAL must be changed manually. If you don’t, the VM might became unstable. I wrote a how-to article on it here.

Number of vCPU together with the VM’s memory allocation is the hardest to correctly size a VMs. I also wrote an article on a complementary whitepaper called VM Memory Sizing Considerations. You can have a look too.

A quick quote from the paper:

In fact, over-allocation of vCPU’s in some VMs will actually cause vm performance problems for that VM and other VMs. On the other hand, the business critical applications running in virtual machines also need to maintain high performance and they need processing power to do so. The last thing a virtualization administrator wants is to have performance complaints from end users. VM administrators face a difficultly in balancing the need to maximize ROI of the server hardware and the requirement for applications to perform optimally.

How to correctly size VMs in an environment?

-   How to approach appropriate sizing of new VMs that need to be deployed
-   How to institute a regular CPU sizing process for the data center
-   How CPU usage works at different levels of the virtualization “stack”
-   How to screen for CPU-based VM performance issues before attempting to optimize an environment
-   What VM performance metrics can provide insights on CPU usage and how to access them

You can download this whitepaper for Free from VKernel’s website here: vCPU Sizing Considerations

Source: vKernel

Enjoy… -:)

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Another free product from VMturboHow-to setup number of cores per CPU in a virtual machinePerformance Best Practices for VMware vSphere 4.1Using Virtual network editor in Vmware WorkstationAutomating with vCenter Server Orchestrator

Vladan SEGET

Vladan is an Independent consultant, vExpert, VCP and owner of this website. This website ESX Virtualization started as a bookmarking site, but very fast found itself many readers and supporters. Feel free to network via Twitter @vladan

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