Can't Enable Hyper Threading in ESX 3.5 on Dell 2900

[smkrt]

I have Dell 2900 with 2.66 GHz X5355 processor, 16 GB and ESX 3.5 installed.

I have enabled Virtualization Technology in the BIOS setting, but the check box of the processor configuration to enable hyper threading is non-highlighted (not changeable) Please check the attached snapshots for the same. Can anyone guide me how can I enable the Hyper threading on my ESX 3.5 in this situation?

Thanks in advance & Byes!

Kazim Raza

[Dave_Mishchenko]

Newer Xeon processors do not include hyperthreading - http://processorfinder.intel.com/DetailsPrinterFriendly.aspx?sSpec=SL9YM.

[smkrt]

Thanks Dave for the response,

So this means that I can not enable hyperthreading on my ESX3.5 and can not have 16 logical processors for my virtual machines?

Please clear me I am bit confused about it.

[VMKR9]

It depends, how many CPUs do you have and how many cores?

[VMKR9]

Sorry just looked at the pics, you have dual quad cores so you can have 8 logical preocessors... it should be enough??

[smkrt]

Dear VMKR9,

Though it could be enought, but If there is someway that I can have 16 processors so why I should not have.

Please help me in finding a wayout of this...

Thanks & Byes!

[VMKR9]

I am affraid you are stuck with 8 unless you buy another 2 quad core processors...

[Dave_Mishchenko]

As VMKR9 mentions this won't be possible. What sort of VMs do you plan to run on this server? With 16 GB of RAM is it likely that you'll start to run out of memory before CPU if you have typical VMs on the server.

How many VMs are you hoping to run and will you be using virtual SMP?

[alex_foradori · Accepted solution]

Dave.Mishchenko is correct, the Intel E5355 (Intel Core technology) does not support Hyper Threading, only the older NetBurst based processors support Hyper Threading. The Virtualization Technology setting in the BIOS needs to be enabled to run 64-bit guests on the server.

Alex

[smkrt]

Dave, I am planning to use this server for Oracle EBS FARM, including all tiers.

Alex, I have enable Virtualziation Technology on the Server and I have 2 Xeon Processors but I still have 8 Logical Processors.

I want to have 16 logical processor on the same server is there any possibility to have it with the current congfiguration?

I must thanks all of you in sorting out the problem.

[Dave_Mishchenko]

ESX or any OS will only see 8 logical CPUs on this system. You would have to add an additional 2 CPU to boost the count to 16.

Your VMs on this host can have up to 128 virtual CPUs - so 128 single vCPU VMs, 64 dual vCPU VMs or 32 quad vCPU VMs or some combination of single, dual or quad vCPU VMs adding up to 128. That said, you'll want to be very careful with dual or quad vCPU VMs as you can have significant performance issues if the ESX host comes under load. Just in case you're wondering, a single VM with 4 vCPUs would only run as faster a 4 physical cores. vCPUs in ESX do not combine the processor cores of the host, so a single vCPU could not use the processing power of 2 physical cores at the same time.

[smkrt]

Dave,

Cau you guide me how can I add 2 CPU to make the processort count upto 16.

Thanks for you last post, it really clear my many point.

[VMKR9]

smkrt, you would have to buy the extra 2 processors, speak to your dell contact and get a quote for adding 2 new processors if you feel you really need them

[Dave_Mishchenko]

Looking at your original post your have a Dell 2900 with is a 2 socket server. To get 16 cores you would need to get something like a Dell 900 / 905 - both of which are quad socket / quad core servers = 16 CPU cores.

Would you be able to elaborate on why you need 16 cores? Perhaps a second ESX host would be needed?

[smkrt]

Dave, I don't have any specific reason for 16 Cores. I just wanted to have it if it is possible within this hardware, I was eager to know about it as i thought it might be some configuration stuff that I am missing and I am unable to locate it.

Thanks for clearing all the point and giving so quick response, thanks to VMKR9 and all who help me in this issue.

[FFK17]

!!!It is not recommended to allocate the same number ov vCPU's as there are physical HOST CPU's to a single VM.!!!

The reason for this is that the way ESX allocates CPU cycles to vSMP VM is that it puts the CPU processing in wait queue until it receives access to all 'n' physical processors. Which for example means that if you have 8 x vCPU's allocated to a VM the VM will have to wait until 8 physical CPU's are available before it's allocated any CPU cycles. As previously mentioned this can have immense performance implications when the HOST comes under load.

As sign of this behaviour is when you see the guest OS maxing out 100% CPU but the Physical CPU's seem to have plenty of CPU cycles to give. Individually they might have plenty of CPU cycles to give but collectively they may not have at one moment in time.

This was all learned from previous experience!!