Solved

CItrix vCPU Allocation in VMware

Posted on 2014-12-11
2
306 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 117

Accepted Solution

by:
Andrew Hancock (VMware vExpert / EE MVE) earned 500 total points
Comment Utility
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
Comment Utility
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

Top 6 Sources for Identifying Threat Actor TTPs

Understanding your enemy is essential. These six sources will help you identify the most popular threat actor tactics, techniques, and procedures (TTPs).

Join & Write a Comment

VM backup deduplication is a method of reducing the amount of storage space needed to save VM backups. In most organizations, VMs contain many duplicate copies of data, such as VMs deployed from the same template, VMs with the same OS, or VMs that h…
HOW TO: Upload an ISO image to a VMware datastore for use with VMware vSphere Hypervisor 6.5 (ESXi 6.5) using the vSphere Host Client, and checking its MD5 checksum signature is correct.  It's a good idea to compare checksums, because many installat…
Teach the user how to rename, unmount, delete and upgrade VMFS datastores. Open vSphere Web Client: Rename VMFS and NFS datastores: Upgrade VMFS-3 volume to VMFS-5: Unmount VMFS datastore: Delete a VMFS datastore:
Teach the user how to edit .vmx files to add advanced configuration options Open vSphere Web Client: Edit Settings for a VM: Choose VM Options -> Advanced: Add Configuration Parameters:

771 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

7 Experts available now in Live!

Get 1:1 Help Now