No CPU core reserved for ESXi Scheduler

[James Hawkins]

Hi,

I have a customer who uses UCS C210 M2 servers with ESXi 4.1 to host UC 8.6 applications including Unity Connection.

The SRND and Docwiki both state that, as the UCS is hosting a Unity Connection system, a core should be reserved for the ESXi Scheduler.

Unfortuantely this requirement seems to have been missed by the install team and the vCPU requirements for the installed machines add up to 8 leaving none available for the ESXi scheduler.

Can anyone tell me the implications of this other than it breaking the Cisco rules for deployment and thus being an unsupported environment.

The kind of things I need to know are will this just effect Unity Connection or all the hosted VMs including CUCM, CUPS etc.

[Chris Deren]

Performance of Unity Connection and support from TAC.  I suggest moving VMs around to accomadate the CPU core appropriately.

HTH,

Chris

[Jaime Valencia · Accepted solution]

In reality, (based on the ESXi/VMWare docs) you need to leave AT LEAST one core unused due to the problems that the CPU allocation mechanism from ESXi causes on real time apps (like all of our UC apps). Basically, it causes jitter for all those apps.

ESXi 5.5 is the very first version that attempts to tackle this problem with real time apps.

HTH

java

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[James Hawkins]

Thanks for the replies.

Java that is really useful information.

Do you know when ESXi 5.5 will be a supported platform for CUCM, UCxn and IM&P and if it will definitely do away with the need for a reserved core?

Cheers

James

[Jaime Valencia]

Sorry, no idea, the BU is still working on it.

Even if I knew, you know that due to CSC policies I couldn't answer it here, that needs to go to the partner community.

HTH

java

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[James Hawkins]

Hi Java,

Thanks - I guessed that would be the case.

The information you have provided has been really useful and is much appreciated

[Richard Ayres]

Hi Jaime,

I note that the latest VM Placement Tool release notes include the following statement in the Known Caveats section:

Unity Connection on ESXi 5.5 no longer requires an "extra core" per server as in ESXi 4.0 thru 5.1. This new sizing rule not yet reflected in VMPT (backlog item).

However, I've been unable to find confirmation that this change has actually made it into the official design guidelines for Unity Connection.  The UC Sizing Guidelines still contains the following:

If there is at least one live Unity Connection VM on the physical server, then one CPU core per physical server must be left unused (it is actually being used by ESXi scheduler).

Am I just looking in the wrong place?

Richard

[Jaime Valencia]

I know that holds true for the BE6Ks as otherwise you wouldn't be able to fit the 5 VMs, I'm pretty sure it will apply for the other deployment models, just wait for the info in the virtualization wiki to reflect that. I'll see what James says next week.

[Brandon Pierce]

From what I saw at the Cisco Geekfest this week, Cisco has removed the core affinity for Unity Connection on 10.6 (10.5.2) on ESXi 5.5 and moving forward to 11.  That makes life a bit easier for those trying to fit everything on one box.  I know that doesn't solve the original problem if you are on anything under that version, but at least it frees up a core.

EDIT: I should have read the above post in small print but it was destroying my eyes :(

[Jaime Valencia]

There was never CPU affinity required for CUC, the old Unity did have that requirement.

[testeven]

Hi Richard,

Thanks for opening a PDI ticket for this. I just want to include the information I gave you on the post so it is available for future reference. According to the link below:

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/connection/10x/requirements/10xcucsysreqs.html#pgfId-360874

"For VMware vSphere ESXi 5.5 and later, you do not need to leave any unused processor core for the ESXi hypervisor / scheduler. The Latency Sensitivity functionality has been introduced to reduce virtual machine latency. "

You need to set Latency Sensitivity to HIGH to be able to leverage the above support. Please refer to the attachment to see where to change this parameter.

Hope this helps!

Regards,

Tere.

Please rate useful posts.

[Richard Ayres]

Thanks for the update Tere.

Great news!

Richard