logical CPU and VM vCPU

[Dongjianhua]

I have an ESXI server, it has 6 logical CPU(the physical CPU does not support HypterThreading), and 5 vCPU have been assigned to the VM's, when i tried to power on a VM with 2 vCPU, i got the following error(see the attachment).

Does it mean the sum of the VM's CPU can not exceed the number of the logical CPU on the ESXi server ?

[Dongjianhua]

Or what is the radio of sum(vCPU) to ESXi logical CPU?

[PCTechStream]

1 Socket with 6 Cores is 6 vCPUs. If you have hyper-threading support on, it will present as twice that (12 vCPUs).

EXAMPLE 1:

CPU Cores describes the number of independent central processing units in a single (chip)

A Thread, is a software of instructions that can be passed through by a single CPU core

# of Processor Sockets = 2

# of Cores per socket = 6

# of CPU Cores = 12

# of Logical Processors = 24

Dual Intel HyperThreaded Six Core Processors would present themselves to anything installed on the bare metal as 24 logical processors.

You might say "I'm confused right now" OK! What is the difference between Processor, Core, Logical Processor?

Processor: It’s the physical components that comes with the server

Core : Is inside your physical processor

Logical Processor : Are Processors and Cores.

So how to count that:

Cores Count = Processor Count * CoresCountPerProcessor

Logical Processor Count = CoresCount * ThreadCount

EXAMPLE 2:

A bi-Quad Core processors server with Hyper-Threading : LogicalProcessorCount = 2 * 4 * 2 = 16

A server with a 12 Cores processor : LogicalProcessor Count = 1 * 12 = 12

A PC with 2 Physical Sockets & 16 Cores per Socket = 32 Logical Processors

The answer to your quest!

Does it mean the sum of the VM's CPU can not exceed the number of the logical CPU on the ESXi server? Possibly!

Start with 1 Processor, 1 Core, if you require, more performance, add another processor, to 2 Processors.

Do *NOT* overallocate processors in the VMs, start with a single processor (socket), 1 vCPU and increase if you require additional performance.

Raul.

VMware VDI Administrator

http://ITCloudStream.com/

[Dongjianhua]

Hi Raul,

Thank you for your explanation.

My question is, if my ESXi has 12 logical CPU, how many vCPU can i assigned to the VM's ? And it there any capped number ?  I mean the total number vCPU of all the VM's .i know it can't exceed 12 vCPU for any one VM.

[PCTechStream]

Like I said before! The answer to your quest! For 12 vCPU

Start with 1 Processor, 1 Core, if you require, more performance, add another processor, to 2 Processors but less VMs.

Do *NOT* over-allocate processors in the VMs, start with a single processor (socket), 1 vCPU and increase if you require additional performance.

VMs: (Min number of machines): 5 / Max number of machines: 8

-- vCPUs: 1

-- Memory: 2048 MB

-- Reserve all guest memory

-- HDD: 25 GB

-- Thn Provision

-- SCSI Controller: LSI Logic SAS

-- Adapter Type: VMXNET3

-- Connect at Power On: YES

-- Select “Datastore ISO File”

-- Connect at Power On: YES

-- Floppy Drive: Remove

POOL for Horizon with View - VMs

Max number of machines: 8

Number of spare (powered on) machines: 6

Minimum number of ready (provisioned) machines during View Composer maintenance operations: 3

Provision machines on demand (Min number of machines): 5

Please confirm if Answered/Helpful this quest! Thanks.

Raul.

VMware VDI Administrator

http://ITCloudStream.com/