?
Solved

Physical to Virtual Machines

Posted on 2013-12-04
7
Medium Priority
?
253 Views
Last Modified: 2016-11-23
I have series of Physical to Virtual machines currently sitting on VMware estate. All of them are running 2k3 and were originally Dell PowerEdge systems with a variety of CPU types.

Some systems have come across with 4 CPUs, other have just one 1. Do all of these systems, now they have become virtual, require CPU allocation to be the same ?

i.e  2 Virtual sockets, 1 core per socket for all ?

Please bare in mind these are only running standard windows services, nothing heavy like SQL or Exchange.
0
Comment
Question by:L-Plate
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
7 Comments
 
LVL 122
ID: 39695741
No, they do not have to be all the same.

Start off with a single  (1) vCPU, and add more if applicable. I would reduce to 1 vCPU socket, and check performance.

It's not often that a VM requires more than 2-4 vCPUs.

vSMP (virtual SMP) can affect virtual machine performance, when adding too many vCPUs to virtual machines that cannot use the vCPUs effectly, e.g. Servers than can use vSMP correctly :- SQL Server, Exchange Server.

This is true, many VMware Administrators, think adding lots of processors, will increase performance - wrong! (and because they can, they just go silly!). Sometimes there is confusion between cores and processors. But what we are adding is additional processors in the virtual machine.

So 4 vCPU, to the VM is a 4 Way SMP (Quad Processor Server), if you have Enterprise Plus license you can add 8, (and only if you have the correct OS License will the OS recognise them all).

If applications, can take advantage e.g. Exchange, SQL, adding additional processors, can/may increase performance.

So usual rule of thumb is try 1 vCPU, then try 2 vCPU, knock back to 1 vCPU if performance is affected. and only use vSMP if the VM can take advantage.

Example, VM with 4 vCPUs allocated!

My simple laymans explaination of the "scheduler!"

As you have assigned 4 vCPUs, to this VM, the VMware scheulder, has to wait until 4 cores are free and available, to do this, it has to pause the first cores, until the 4th is available, during this timeframe, the paused cores are not available for processes, this is my simplistic view, but bottom line is adding more vCPUs to a VM, may not give you the performance benefits you think, unless the VM, it's applications are optimised for additional vCPUs.

See here
http://www.vmware.com/resources/techresources/10131

see here
http://www.gabesvirtualworld.com/how-too-many-vcpus-can-negatively-affect-your-performance/

http://www.zdnet.com/virtual-cpus-the-overprovisioning-penalty-of-vcpu-to-pcpu-ratios-4010025185/

also there is a document here about the CPU scheduler

www.vmware.com/files/pdf/perf-vsphere-cpu_scheduler.pdf
0
 
LVL 28

Expert Comment

by:jhyiesla
ID: 39695744
No, there's no reason to have them sucking down excess CPU if it's not needed.  And you should be able to adjust down without an issue, although it will require you to take the VM's down to make the change.
0
 

Author Comment

by:L-Plate
ID: 39695995
Thanks for you responses both of you.

Hancocka, which section are you referring to change ?

Is it Number of Virtual sockets or Number of cores per socket ?

Would comparing a physical machines hardware platform been taken into consideration for CPU allocation ? i.e a 2008 box has a 2 physical CPUs, each being quad cores.

Would it be safe to transfer that config virtually ?
0
The Eight Noble Truths of Backup and Recovery

How can IT departments tackle the challenges of a Big Data world? This white paper provides a roadmap to success and helps companies ensure that all their data is safe and secure, no matter if it resides on-premise with physical or virtual machines or in the cloud.

 
LVL 122
ID: 39696016
change to 1 vCPU socket. (cores is usually altered for licensing reasons).

always use 1 vCPU and adjust.
0
 

Author Comment

by:L-Plate
ID: 39700484
Ok

So I can adjust virtual sockets to whatever I need in regards to performance and reduce the cores per socket to 0 as this is purely for licensing requirements.

correct ?
0
 
LVL 122

Accepted Solution

by:
Andrew Hancock (VMware vExpert / EE MVE^2) earned 2000 total points
ID: 39700505
Correct (cores = 1)
0
 

Author Closing Comment

by:L-Plate
ID: 40192042
thank you, sorry for the delay
0

Featured Post

Want to be a Web Developer? Get Certified Today!

Enroll in the Certified Web Development Professional course package to learn HTML, Javascript, and PHP. Build a solid foundation to work toward your dream job!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Restoring deleted objects in Active Directory has been a standard feature in Active Directory for many years, yet some admins may not know what is available.
In this article, I show you step by step with screenshots to assist you - HOW TO: Deploy and Install the VMware vCenter Server Appliance 6.5 (VCSA 6.5), with some helpful tips along the way.
Teach the user how to configure vSphere Replication and how to protect and recover VMs Open vSphere Web Client: Verify vsphere Replication is enabled: Enable vSphere Replication for a virtual machine: Verify replicated VM is created: Recover replica…
How to Install VMware Tools in Red Hat Enterprise Linux 6.4 (RHEL 6.4) Step-by-Step Tutorial
Suggested Courses

743 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question