BE7000, UC Applications and hyperthreading

[raziel78kain]

Hello,

we have a BE7000, which has arrived with the various Cisco UC Applications (CUCM, CUC, ...) preloaded on it.

We have noticed that the hyperthreading is active on the server, by default.

Previously, we had to deal with some BE6000s (preloaded with the UC Apps), and in those cases the hyperthreading was inactive...

So, our question is the following: is the Cisco policy for the hyperthreading on their UCS server different between BE6000s and BE7000s, if they are used for their UC Applications?

TIA and regards.

[Rajan · Accepted solution]

Hi,

Hyperthreading can be enabled if there are enough resources available as per the docwiki and if the below conditions are met:

If "Hyper-threading" BIOS option is available (and the CPU supports hyper-threading), UC recommends enabling.

• Note that the resultant "Logical Cores" do not factor into UC sizing rules for co-residency. UC still requires mapping one physical core to one vcpu core (not to one "Logical Core").

http://docwiki.cisco.com/wiki/UC_Virtualization_Supported_Hardware

So even with hyperthreading enabled VM vCPU core should be matched only to the physical cpu cores avl as mentioned in the sizing requirements:

http://docwiki.cisco.com/wiki/Unified_Communications_Virtualization_Sizing_Guidelines

Must map 1 VM vCPU core to 1 physical CPU core.

• For example, if you have a host with 12 total physical cores, then you can deploy any combination of virtual machines where the total number of vCPU on those virtual machines adds up to 12.
• The requirement is based on physical cores, not logical cores.
  • Logical cores may exceed physical cores if CPU hyperthreading is used. See UC Virtualization Supported Hardware for recommendation on hyperthreading and other BIOS settings. See screenshot below for physical cores vs. logical cores (as viewed from either VMware vCenter or vSphere Client) for a UCS C220 M3S server with CPU hyperthreading DISABLED. If hyperthreading is ENABLED, you will see 16 logical cores despite only 8 physical cores, but UC sizing rules are still limited by 8 physical cores

HTH

Rajan

Pls rate all useful posts

[raziel78kain]

Hello Rajan,

so, we can keep the hyperthreading active, but we are limited to map a maximum of 12 cores for our VMs (in our scenario), even if there are 24 logical cores, due to hyperthreading. Is it right?

Thanks and regards.

[Rajan]

Yes. But you could use only the actual physical cores avl and this limitation is not due to hyperthreading being enabled but due to the limitation of UC applications that there has to be a 1:1 mapping with the physical cores.

HTH

Rajan

[raziel78kain]

Thanks again Rajan.

Just a curiosity: what does "avl" mean? :-)

Regards.

[Rajan]

Sorry its Available :) 

[raziel78kain]

OK, thanks! :-)

I thought that "avl" was an acronym... :'-)

[Manish Gogna]

Avl means "available" in this case.

Manish

[niks]

I understand what you have explained and Cisco Virtual Collaboration sizing guide states the same. But, one thing is not clear to me: for example, when you order BE6000 or BE7000, they come from factory with hyperthreading enabled which gives you double the vCPU versus the physical CPU. To match the 1vCPU : 1 pcore, you must manually double the vCPU in OVA templates for collaboration applications, right? If that is true, Cisco pre deployed collaboration applications, which come with BE servers partially installed don't have doubled vCPU, so if I am not wrong, even Cisco don't follow the rule 1vCPU:1pcore?

Thank you