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riker82
Enthusiast
Enthusiast

4 x VCPUs Vm - High Cpu Ready - High Cpu System

Hi everybody,

Our VI farm is composed of 9 x hosts (PE2950 & IBM HS21 blade) with serveral datastores and RDM Luns: On these hosts we virtualized over 176 Virtual machines (Windows 2003, Windows XP, Linux)

One months ago we decided to p2v all our exchange severs (4 x mailbox servers, and 1 x mta connector, Windows 2003 Enteprise SP2, Exchange 2003 SP2). All of them with 4 x cpus and 4 gb of memory containing over 1300 mailboxes in total (more or less). Each one has a Raid 10 Rdm Lun for databases, Raid 10 Rdm for Transaction Log and a Raid 5 Rdm Lun for Dump (Our storage is a Clariion CX3-40).

Some of them in some situations become freezed (even the console) and in performance tab we can see very high cpu ready value (125.000 ms!!) and very high cpu system (152.000 ms!!!) on the first assigned cpu (cpu 0). In attach you can see the screenshot of what I'm trying to explain

1. Anyone can explain me why? Is it the overcommitment of 4 Vcpus?

2. Anyone can explain me why in some condition, I've some "hole" in performance logging (see exc1002cpu_usage.jpg_ attach)?

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AWo
Immortal
Immortal

How many CPU cores does the host have where the servers are running on?


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AWo

VCP / vEXPERT 2009

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depping
Leadership
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Looking at the numbers you are overcommitting on vCPU's vs Physical Cores, this will cause scheduling. And with a 4 vCPU VM, which will be utilized by Exchange, scheduling will be hard cause they will need to be scheduled at the same time. I would suggest scaling out instead of scaling up.

I would suggest reading the articles/documents by Scott Drummonds for more detailed info on this : http://communities.vmware.com/people/drummonds

Especially this one on ready time:http://communities.vmware.com/docs/DOC-7390

Duncan

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TomHowarth
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from what you have posted and the diagram, it would seem that you are seriously suffering from CPU contention. the way that ESX services vSMP guests is that it will requrie a free core to be available for each of the vCPU;s in the Guest. as a test drop the CPU count to 2vCPU in the Exchange servers, I would almost guarentee you will see a serious reduction in CPU ready times

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Tom Howarth VCP / vExpert

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Blog: www.planetvm.net

Contributing author for the upcoming book "VMware Virtual Infrastructure Security: Securing ESX and the Virtual Environment”.

Tom Howarth VCP / VCAP / vExpert
VMware Communities User Moderator
Blog: http://www.planetvm.net
Contributing author on VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment
Contributing author on VCP VMware Certified Professional on VSphere 4 Study Guide: Exam VCP-410
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AWo
Immortal
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Yep, that's what I was thinking about, too.


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AWo

VCP / vEXPERT 2009

vExpert 2009/10/11 [:o]===[o:] [: ]o=o[ :] = Save forests! rent firewood! =
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riker82
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Enthusiast

all our hosts have 4 x cores al minum and 8 x cores at max!

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depping
Leadership
Leadership

Again, with that amount of vCPU's and that amount of Cores you will run into scheduling issues for sure. I would suggest creating more vm's with less vCPU's. (2 vCPU's max.)

Duncan

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riker82
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Thank you everybody for your help. We were planning to reduce all of Exchange vms to 2 Vcpus (2 of them were already reduced)

1) So you concern that this vm is suffering of CPU contention. One question: What's the meaning of CPU system value in performance tab?

2) Can Affinity resolve my issue?

All the experiments that I can found on the internet of Exchange on Vmware, are of "dedicating" a physical host for all exchange servers. Should I do it? with affinity or not (I know that I can loose DRS features)?

thanks

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