ESXi 5.1 VM Odd NUmber of CPU Sockets

I have often wondered why VMware lets you assign a odd number of cpu sockets to a VM when this is not a option with a physical server. I have always like to assign even number but I want to get other people thoughts on this. Is there a performace difference between odd and even sockets counts
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
I believe it is to do with the physical design of motherboards, and the chipsets and memory managers, and RAM Banks.

On a physical server, often if you do not populate both CPU sockets, there is a terminator socket, in place of the empty socket, (no terminator present, the server often does no power up) also it is common for memory banks to be assigned a processor, and also PCI sockets (express as well) are assigned to a CPU.

So manufacturer design constraints, these constraints do not exist in the virtual world.

As for performance issues between odd and even, usual rule of thumb, increase vCPU as and when required.

One of the benefits of virtualisation, and how granular it can be, the same could be said of memory addition, in a physical server depending on a server, the minimum size DIMM, these days could be a 2GB DIMM (if applicable - you cannot cut it in half and use it), but VMware allows you to increase and decrease memory in much smaller increments, but how many just add memory to a VM, by the 1GB to 2GB increment!

Again, in a virtual environment, we are not contrained by the physical parameters, in the virtual realm, we can allocate the EXACT resources we require, to get optimum performance! (and we should!).

Have you ever run a Efficiency Wastage Report across your servers ?

To see how much Memory and CPU can be recovered ?

See here....

we went on site and found this...

When they saw this report, their jaws dropped and went quiet....

vROPS Report
47% of VMs were over sized.
33% of VMs were powered OFF.
20% of VMs were idle.

Mainly too many vCPUs and too much memory allocated to VMs, what have I said about VMware Admins and too many vCPUs, because they can!

e.g. 4 vCPUs instead of 1 vCPU.

It's all there in the detail per VM, when you drill down.

Management:- Don't let your VMware Admins fool you, try vCOps or vROps today for free!

It's also a question here:--

vRealize Operations Manager 6.0 - are you using it? Do you recommend it?

So by allocating the resources we actually need, we can stop over provisioning, and saving resources and money!

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compdigit44Author Commented:
Great Explanation as always!!!!
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