Solved

CItrix vCPU Allocation in VMware

Posted on 2014-12-11
2
324 Views
Last Modified: 2015-01-28
We have a few Citrix XenApp (6.x) servers running on a VMware estate. The underlying hardware has multiple CPUs and cores.

I read somewhere that it is not advisable to simply give Citrix all available vCPUs as this can actually have a negative impact on performance rather than a position one.

Can anybody advise on the best practice?
0
Comment
Question by:Hypervizor
2 Comments
 
LVL 118

Accepted Solution

by:
Andrew Hancock (VMware vExpert / EE MVE) earned 500 total points
ID: 40494249
Yes, I would allocate 2 vCPU (sockets not cores), maybe possibly 4 vCPUs.

but to be honest, you are better, with 2 vCPU servers, and more of them, in the farm.

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

https://blogs.vmware.com/vsphere/2013/10/does-corespersocket-affect-performance.html
0
 
LVL 36

Expert Comment

by:Carl Webster
ID: 40503309
Project Virtual Reality Check says you get best results with either 4 vCPUs or 8 vCPUs.

http://www.projectvrc.com/white-papers

http://www.projectvrc.com/white-papers/8-phase-2-hyper-v-2008r2-vsphere-4-xenserver-55-v20/file
0

Featured Post

Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
Non-Destructive Way of Extending Volume 15 65
esx multi vlans 3 63
VMware Horizon View SSL problems 1 26
Standalone converter (Shrinking process) 4 55
Exchange server is not supported in any cloud-hosted platform (other than Azure with Azure Premium Storage).
Last article we focus in how to VMware: How to create and use VMs TAGs – Part 1 so before follow this article and perform the next tasks, you should read the first article how to create the TAG before using them in Veeam Backup Jobs.
This Micro Tutorial walks you through using a remote console to access a server and install ESXi 5.1. This example is showing remote access and installation using a Dell server. The hypervisor is the very first component of your virtual infrastructu…
This demo shows you how to set up the containerized NetScaler CPX with NetScaler Management and Analytics System in a non-routable Mesos/Marathon environment for use with Micro-Services applications.

867 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

Need Help in Real-Time?

Connect with top rated Experts

21 Experts available now in Live!

Get 1:1 Help Now