Solved

VMWare, vCPU allocation for VM

Posted on 2012-03-17
4
783 Views
Last Modified: 2012-03-17
If I have a 16 core server, and I allocate only a single VM, and that VM is only allocated 8 vCPU, ......

... will that VM run with only 8 cores, or will VMWare detect that more cores are available and steal cores and give it to the VM, therefor that VM is running with more than 8 cores ?

Thanks
0
Comment
Question by:Los Angeles1
  • 2
4 Comments
 
LVL 40

Expert Comment

by:coolsport00
ID: 37733534
The VM will use what it needs at any given time. Unless you use 'CPU affinity', which is a config for a VM to use explicit CPUs, the VM will use whatever is available at any time when the VM needs compute resources. I highly recommend reading over the CPU Scheduler whitepaper:
http://www.vmware.com/files/pdf/techpaper/VMW_vSphere41_cpu_schedule_ESX.pdf

~coolsport00
0
 
LVL 117

Accepted Solution

by:
Andrew Hancock (VMware vExpert / EE MVE) earned 500 total points
ID: 37733547
if you have allocated 8 vCPU.

8 vCPU = 8 physical cores on the physical host. in simple terms.

It will never run with more than 8vCPUs.

What license do you have?

because the license will limit you to a max of 8 vCPUs!
0
 

Author Comment

by:Los Angeles1
ID: 37733598
Do the 2 posts above disagree.  The first says the scheduler will use whatever it needs, (so I assume that the VM will use extra cores that are not being utilized, even if it exceeds the limit of vCPU assigned to it)  the second says 8 vCPu means only 8 physical cores.

Am I misunderstanding your answers (I know you both generally agree, so I must misunderstand something)
0
 
LVL 117
ID: 37733608
if you assign 8vCPUs, the hypervisor WILL ONLY ever execute your VM on 8 Cores.

(they may not be the same cores, through the process of the execution!)

e.g. the scheduler looks at ALL cores every 20ms, you VM may run on the same 8 Cores, or it could change to another 8 Cores, but by defination of 8vCPUs, it will never be more than this.

AND, if you do not have a license to use 32 vCPUs, license restricts you to 8 Way SMP.
0

Featured Post

Complete Microsoft Windows PC® & Mac Backup

Backup and recovery solutions to protect all your PCs & Mac– on-premises or in remote locations. Acronis backs up entire PC or Mac with patented reliable disk imaging technology and you will be able to restore workstations to a new, dissimilar hardware in minutes.

Join & Write a Comment

Suggested Solutions

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…
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 delpoy the vCenter Server Appliance and how to configure its network settings Deploy OVF: Open VM console and configure networking:
This Micro Tutorial steps you through the configuration steps to configure your ESXi host Management Network settings and test the management network, ensure the host is recognized by the DNS Server, configure a new password, and the troubleshooting…

757 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

19 Experts available now in Live!

Get 1:1 Help Now