ESXi

I am very new to running vsphere on a server and was wondering how I can best allocate resources to my VMs. I am running light chess game simulations on each VM, and want 16VMs actively 24/7, with a dozen others switched on, but not running any processes. My main concern is that the CPU seems to be struggling at the moment. If I allocate a VM 1 socket and 1 core, the CPU hits 100% quite easily for that VM. If I allocate it 1 socket and 2 cores, it seems to do alright. Would I be able to run this many VMs with 2 cores each on my server ? It has 2x Intel® Xeon® E5620 (4x 2.4 GHz. with Hyper Threading).

See the attachment for the VM settings I will use on each VM, even though I might allocate 4gb memory to each, since I can easily upgrade to 128GB memory on my host server. 

Really appreciate any help!

To be perfectly honest, it depends how active the CPUs are within those guest VMs.

You are right to over-commit CPU cores though. ESXi handles this very well.

What I would do for a BASIC answer is add up all the "GHz" for the VMs you want to run, so: 16 VMs x 2 cores at 2.4GHz each = 76.8GHz

Then

Add up the GHz available on the ESXi server(s) 2x 4x 2.4GHz = 19.2GHz

So you would have 19.2GHz available on the ESXi host but you would want to run 76.8GHz on that ESXi hosts.

A rough calculation means that on average, VMs would need to be running at less than 25% CPU for this to work without contention 76.8GHz / (100/25) = 19.2 GHz

This is VERY approximate but should give you an idea of what's possible.

Hope this help.

Thank you I can work with that as starting point. Will let you know if anything comes up.

If your server having HT feature , it will help you allocate the resources more useful.

Check above image  2 proc x 8 Cores and by HT it doubles to Logical processor = 32   , it will help to provision more VMs with allocate resources . It doesn't mean you can  have 32 CPU its logically available and resources will shared and manged across vms with vsphere techniques .

Intel® Xeon® Processor E5620 (12M Cache, 2.40 GHz, 5.86 GT/s Intel® QPI) Specifications

E5620 having 4 core and HT available .

2 x 4 x 2 = 16 Logical CPU  , 16 x 2.4 = 38.4   .

I hope this info will be help full