Creating a VM---virtual Sockets vs Virtual Cores

[jedijeff]

I am not sure where to post this.

I am a bit confused on when creating a VM you now get an option to choose number of sockets or number of cores. Ie 4 socket 1 core, or 2 socket 2 cores.

I have heard different reasons from different vmware trainers

From it is only for licensing it doesn't matter. To it must match your numa configuration or you will have performance issues.

To me I always thought it was just 4 cores for vm--no matter how it got there.

Could someone explain this to me please.

[admin · Accepted solution]

Hello

numa configuration does affect your performance.

these blog's should be helpful

Does corespersocket Affect Performance? | VMware vSphere Blog - VMware Blogs

http://frankdenneman.nl/2013/09/18/vcpu-configuration-performance-impact-between-virtual-sockets-and...

Please let me know if this does not answer your question.

Thanks,
Avinash

[taylorb]

Another consideration is that if you use CPU hot add, you cannot change the number of cores, only number of sockets (while the VM is running).   And if you change sockets, it will be another vCPU with the same number of cores as the first.

For example, if I had a single processor 6 core VM and I hot-add a second socket, I am going to end up with Two 6 core processors.   That's a big jump. 

If I had 3 dual core CPU and I hot add a fourth socket, I end up with 4 dual core processors. Or I could do 5 or 6 or 8 dual cores, etc.  It gives me a bit more flexibility when I keep the core count lower.