Better performance: 2 CPU 4 core, or 1 CPU 8 core

[kjstech]

For a VM running SQL, our budget can stand to licence 8 cores.  Now what do you think would be better performance on the VM?

A configuration of 1 virtual CPU with 8 cores?  or a configuration of 2 virtual CPU's with 4 cores?  The net result is still the same (1 x 8 or 2 x 4).  Either way I figure we would be in compliance with SQL licencing.

The host is running ESXi 5.0.0, 1489271.

vSphere 5 enterprise plus for 2 physical cpus

Dell PowerEdge R620

Intel Xeon E5-2650 @ 2 GHz

2 Processor Sockets

8 cores per socket

32 logical processors

Hyperthreading Active

The VM is Windows Server 2008 R2 Datacenter.

[JPM300]

When it comes down to the scheduling 1vCPU with 8cores is pretty well the same thing as 2vCPU's with 4 cores.  When it makes a request for the CPU its still going to do the same kind of scheduling in the hypervisor to find a sutiable CPU/Core to run the instruction set on.

However SQL typically likes multiple CPU's so I would go with 2VCPU's with 4cores personally, but thats just my expereience.

Also the multiple cores per vCPU has been in ESXi for a long time now but it wasn't till 5.X until they brought it into the GUI.  It used to be an advanced configuration option in the VM prior to 5 to get this and was typically used to get around OS limitations.  For instance Windows Server 2003 Standard was capped at 2 or 4CPU.  So if you wanted more then that you had to use vCPU cores.

Hope this helps