Hyperthreading core count

[tmcd35]

We have two dual processor XEON servers. We are looking to replace the processors with faster 3.2Ghz models. So we will have a total of 4 cores across two servers plus Hyperthreading.

I have read that a recommended max of 8 VMs per core, which gives us 4x8 = 32 servers. But, how does HT mix in with this? Would you count HT as effectively half a core so (4/2)*8 = 16 additional servers, giving us a theoretical max of 48 servers across these two boxes.

I know this is all purely guess work and depends heavliy of the servers being virtualised. We actually only need to virtualise around 10 servers at the moment but as a selling point to the money men I was wondering what kind of millage to expect out of our existing servers before we should look at replacing them.

Our servers are a mixture of Databases, Intranets, Print server, file servers - usual mix for a school environment.

Terry.

[Starlionblue]

tmcd35,

Currently dual (and quad) core Intel processors do not implement hyperthreading. This is true both of Core 2 and Xeon. Each core is "single threaded".

See here http://www.newegg.com/Product/Product.aspx?Item=N82E16819117103 for an example.

[tmcd35]

We have old XEON machines which I have sourced the correct processors and RAM for. They are 3.2Ghz Single Core, Hyperthreaded processors. I believe the BUS speed is 533mhz on these models (might be 400mhz, can't remember 100%).

We currently have 2x 2.8Ghz in one and 2x 2.2Ghz in the other server. They are single (no vmware) servers with 4Gb and 2Gb Ram respectfully. The plan is to upgrade these servers to 2x 3.2Ghz and 8Gb Ram each.

The question is how much extra millage would we get out of HT? We will have a total of 4 physical core and 8 logical cores. If we do not ude vSMP (no need to), in theory how many single core virtual machines could we run total across the to hosts?

Based on a rec. max of 8 VMs per core, would we have 32 VM's (4 cores), 48 VM's (counting HT as half a core), 64 VM's (counting HT as a full core)?

Like I said above we are only really needing to Virtualise around 10 physical servers at the moment, but we want to give the bean counters some idea of the scalability of what we are proposing.

Thanks

Terry.

[VirtualNoitall · Accepted solution]

Hello,

HT will help but I doubt it would even be at half a core. Remember, even 8 is just a guide and you can get more or less depending on load. Maybe 1 VM per server?

I would also steer clear of vSMP > 2 if you have two physical sockets. HT doesn't count in this instance.

[Starlionblue]

As mentioned earlier, dual and quad core Intel processors do not support Hyperthreading so its a moot point.

[tmcd35]

i was wondering wether or not I should rise to this, but what the hell consider myself well and truely baited...

Startionblue - PLEASE READ THE POSTS! We are not looking at either dual or quad core processors, we can't afford to! We are using SINGLE CORE 533mhz BUS XEONS WITH HT.

We have the ability to upgrade or 2.2Ghz/2.8Ghz processors to 3.2Ghz - Thats single core HT Xeons as that all the motherboard will support.

Speaking of which the motherboard supports 2 processors (SMP) to thats 2 cores and 4 threads per host server, or 4 cores and 8 threads across 2 host servers.

Cheers

[Starlionblue]

Sorry about that. When you talked cores my brain clicked and said "multiple cores".