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assanemd
Enthusiast
Enthusiast

Changing the number of vCPUs of a VM is it recommended ?

i'm asking if changing the number of vCPU affected to a VM is recommended. The VMs are win2003, 2008 and linux centos. i ask for this because i faced lots bsod (blue screen) on windows VMs on which the the number of vCPUs was changed. 

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f10
Expert
Expert

Hi,

If you are trying to fix the BSOD issue then changing the number of vCPUs would either have not impact or may be a shot in the dark. I wouldn't change the number of vCPUs until I am facing any specific vCPU contention or performance issues. I would troubleshoot the BSOD issue and try to get to the root cause with help of VMware and Microsoft. You may also use the following KBs while troubleshooting BSOD issues:

VMware KB:    Identifying critical Guest OS failures within virtual machines 

How to read the small memory dump file that is created by Windows if a crash occurs

Alternatively, check if appropriate HAL is used for the Windows VMs after changing the number of vCPUs, more information can be found here VMware KB: Modifying the Hardware Abstraction Layer (HAL) for a Windows virtual machine

-Arun

http://highoncloud.blogspot.in/

About VMware Virtualization on NetApp

Regards, Arun Pandey VCP 3,4,5 | VCAP-DCA | NCDA | HPUX-CSA | http://highoncloud.blogspot.in/ If you found this or other information useful, please consider awarding points for "Correct" or "Helpful".
DavoudTeimouri
Virtuoso
Virtuoso

vCPU number is depended to your VMs or user requirement.

For example, if your VM is working with high CPU usage in most of times, you can increase vCPU number to 2x of current vCPUs.

But you should consider that each OS and each edition of OS is supporting limited number of CPU and cores.

For example, Windows 2003 Standard edition is supporting 4 CPUs.

Also some applications licensing is based on CPU socket.

Also it's recommended, you don't change vCPU configuration after installing OS on virtual machine.

Operating systemNumber of processorsPhysical RAM
Microsoft Windows Server 2003, Standard Edition44 gigabytes (GB)
Microsoft Windows Server 2003, Standard x64 Edition432 GB
Microsoft Windows Server 2003, Enterprise Edition864 GB
Microsoft Windows Server 2003, Enterprise x64 Edition81 terabyte
Microsoft Windows Server 2003, Datacenter Edition3264 GB
Microsoft Windows Server 2003, Datacenter x64 Edition641 terabyte
Microsoft Windows XP Professional24 GB
Microsoft Windows XP Professional x64 Edition2128 GB
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