Virtual Machines and HyperThreading

[Djinni]

Wanting to know... (Preferably from people who've tried both setups) how well Virtual Machines work with HyperThreading enabled. Weather there is any performance difference between having HT on or HT off.

Programs of use:
VM Player,
VM Workstation,
VirtualBox,

[Deleted]

I've tried Windows XP on my Mac using Parallels Desktop, could you please tell me what Hyperthreading is so I maybe can help you. I've been lurking around on the computer forums couple of days because I'm trying to learn more about computers.

[Djinni]

I've tried Windows XP on my Mac using Parallels Desktop, could you please tell me what Hyperthreading is so I maybe can help you. I've been lurking around on the computer forums couple of days because I'm trying to learn more about computers.

Intel® Hyper-Threading Technology (Intel® HT Technology)¹ uses processor resources more efficiently, enabling multiple threads to run on each core. Intel® HT Technology increases processor throughput, improving overall performance on threaded software.
An Intel® processor and chipset combined with an OS and BIOS supporting Intel HT Technology allows you to:

• Run demanding applications simultaneously while maintaining system responsiveness
• Keep systems more secure, efficient, and manageable while minimizing impact on productivity
• Provide headroom for future business growth and new solution capabilities#

(Some blurb from intel...)

[Deleted]

I've tried Windows XP on my Mac using Parallels Desktop, could you please tell me what Hyperthreading is so I maybe can help you. I've been lurking around on the computer forums couple of days because I'm trying to learn more about computers.

Hyperthreading is Intel's name for a technique called "Simultaneous Multi-threading". Basically its a technique to push two separate threads onto a single processor core. This can reduce the amount of time that the core 'idles' and as such increase throughput.

[Deleted]

Okay, that looks cool, havn't tried it tho.

[Djinni]

Okay, that looks cool, havn't tried it tho.

but as has been pointed out in lots of threads on the forums... not all programs make good use of threading... so they can't take advantage of it.

[vesseblah]

Wanting to know... (Preferably from people who've tried both setups) how well Virtual Machines work with HyperThreading enabled.

Havent tested, but all enterprise level server documentations tell you to turn HT off. It's simply because the fake cores mess up with the VM manager's scheduling and resource allocation mechanics if the computer thinks there's more cores to hand out for VMs.

[Sixthshot]

This all depends on whether your VM program can support multiprocessing or not, and of course whether you machine is a multiprocessor machine also.

In work I have a couple of VMs running hyperthreads due to the amount of work that gets passed through them (We are using them as servers so we can split down the processor even more, this allows for easier resource management)

Best way to see, if make an image of the VM machine as a back up and then have a play.

If it doesn't work just go back to the image you took

[Neeko]

i've given you my opinion before, and your 'not all programs make use of it' is kind of the bigger question here

I have never ran more than 1 VM on my machine, but IF and thats IF a VM OS works like a regular OS then Hyperthreading is teh win, esp when u run 5 of them,

If they do not work like regular operating systems however, then ur it would not matter I guess and u can save the money

So the bigger question is, does an OS running on a VM work like a regular OS?

[antitux]

I've done a lot of server virtualization, and until the Nehalem-style (Core i5/i7 on desktop) line of processors came out, we'd always turn hyperthreading off if it was enabled. Nowadays that's not an issue. Leave it on. It does make a pretty big difference on performance.

Also, all current VM technologies and OSs support multiple processors/cores.

What exactly are you virtualizing?

[Djinni]

What exactly are you virtualizing?

Multiple Operating Systems, Simulating various network configurations with different operating systems, simulating various network configs and backup plans etc...
Lots of experimenting with various OS' in different setups.

[Sykotic13]

Multiple Operating Systems, Simulating various network configurations with different operating systems, simulating various network configs and backup plans etc...
Lots of experimenting with various OS' in different setups.

Medium-short answer is yes you should get the i7-2600k over the i5-2500k if you are going to be running VMware Workstation to simulate an ESX/VCenter environment (did I guess right?). One benefit that I haven't seen mentioned is that with HT on you have 2 threads per core. Those threads are presented in the host OS as a logical processor. So, Windows presents as having 8 logical processors. I use this to assign multiples processors per VM knowing that VMware thinks there are 8 processors total to be used. It will load balance well on them. At least that has been my experience.

TL;DR answer: If you use VMware you want the i7-2600k and HT turned on.

Picture of what I mean about logical processors linked below. This is from msinfo32 on my machine:
http://img62.imageshack.us/img62/953...1jul201357.jpg

[SoCal]

Consider throwing ESXi Free on? Its not really what your asking but if you're looking (I'd guess the same) of emulating ESX/vCenter then it could be an option as well.

[Sykotic13]

Consider throwing ESXi Free on? Its not really what your asking but if you're looking (I'd guess the same) of emulating ESX/vCenter then it could be an option as well.

Not exactly. ESXi would allow him to put the machine in an existing VCenter. However, what I was referring to is using VMware Workstation to create several virtual machines that run VCenter along with a virtual machine that runs a (virtual) SAN like OpenSAN. One of VCenter's requirements is SAN storage. In VMware Workstation 4.x you could run an ESX sandbox, but they took that away in version 5.x and 6.x. They brought it back in version 7.x so people are creating the ESX sandboxes now in order to test certain VCenter features and to help study for CCIE testing.

[Cyanotical]

iirc the free ESXi is limited to 6 cores, whether this make a difference to you idk, im not exactly sure what you are trying to accomplish, but i have built several ESXi machines with dual xeons w/HT and they run fine, they actually run better then a server with dual 12c opterons