Underutilized logical cores on ESXi 3.5 U5

I am using ESXi 3.5 U5 on 2 socket cpus with HT which gives 4 logical cores. My VM is running Windows 2003 Server with 2 vCPU each. On one physical server I have two vm running and on another physical server only one vm. What I noticed is by default the logical cores 1 and 3 on both physical servers is grossly underutilized compared to logical cores 2 and 4. Ratio of over 2:1. Is there setting to allow for all logical cores to be used? Should I increase the vCPU on the vm from 2 to 4? One is a domain controller, one is multipurpose WSUS, antivirus server (using SQL and MYSQL) and the third is a web server with a SQL server as well.

Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Matthew EnglandTechnology ConsultantCommented:
Unless you require additional CPU resources on the VM, refrain from increasing the vCPU's for it. Adding additional resources to a server, also increases the overhead resources that are utilized by the host, which will reduce your total available VM capacity & limit your failover capabilities in HA.

Unless your experiencing performance problems, let VMWare continue to manage the resource allocation, however if you need to you can adjust the allocations.

Refer to the sections on Hyper-threading and Using CPU Affinity.

I hope this helps.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
autocribAuthor Commented:
This will apply to ESXi 3.5 as well?  The thing is on the vSphere 4.0 version.. all the cores are used equally.  I can't upgrade to the 4.0 version because these physical servers are 32-bit and 4.0 reuires 64-bit CPUs.
Matthew EnglandTechnology ConsultantCommented:
Yes. CPU Affinity also applies to 3.5.
Select the Virtual Machine and click Edit Settings.
Click on the Resources Tab.
Click on Advanced CPU. Select the Run on Processors option, and select the desired processors.

Keep in mind that you want to avoid this type of configuration if you're using DRS.
autocribAuthor Commented:
It turns out adding additional vCPU to the VM didn't help much with overall performance as oppose to using 2 vCPU on a HT enabled physical box, since the HT only simulate additional cores and ESXi prefers to use physical cores and not logical cores, especially logical core derived from HT.  My server load for that VM is just too much from the current hardware.  Will upgrade to faster hardware.  Thanks
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft Server OS

From novice to tech pro — start learning today.