HA Cluster Mismatched Hardware CPU Sizing

Current Scenario

2 Hosts both with 2 quad core 2.93ghz processors.

Future Scenario

Upgrade both hosts to 4 quad core 2.93ghz processors
Add another host with 4 processors to the HA cluster

Problem is that the matching server hardware is no longer available. So the question I have...

Is it better to find hardware with matching total Ghz regardless of cores?
example. 4 cores x2.93=11.72 and 6 cores x2.0=12

Or is better to find hardware with individual core speeds as close to each other as possible?
example 4 cores @ 2.93 and 6 cores @ 2.66

I don't know if this will be important or not but currently running vSphere4 with plans to move up to 5 in the coming weeks.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Find hardware with more cores. Because in vSphere 5.0, you are not restricted up to 6 cores anymore, you are restricted on vRAM.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You'll always be able to use EVC mode, to build the cluster for DRS, vMotion if applicable.
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I do at home have vmware vsphere setup inside vsphere esx server on different achines in two esx servers and have the virtual vsphere servers in a cluster I know this will add a layer of compexity but it will mean you can do clustering in different servers
Do you need all that CPU power? I ask because I have servers ranging from two dual core CPU with 16 GB RAM to dual quad core with 144 GB RAM, and no host is ever at more than 20% CPU, and usually closer to 10% or less. I would double check your CPU utilization before adding more CPU. I believe that you only need to match the BRAND of processor in your VMWare HA cluster.
midwestexpAuthor Commented:
I'm more worried about the cluster going out of balance if I enable admission control at a later date. I had read that being resource heavy on one hardware can effect the reserved capacity on smaller hardware. So I'm trying to find what the balance point on CPU is, Core count or total Ghz, so that I can keep the cluster relatively balanced. If my thinking is wrong, please advise.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
That would be HA slots.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Should have explained which is based on CPU cycles, so GHz!

Check here


and Duncan explains really well here


and if you've not got his Book or eBook you should have a read!

VMware vSphere 4.1 HA and DRS Technical deepdive (Volume 1)

By Duncan Epping and Frank Denneman


ISBN-10: 1456301446
ISBN-13: 978-1456301446

Written by Duncan Epping and Frank Denneman, both of whom are Consulting Architects at VMware and are perceived by the industry as Subject Matter experts on VMware High Availability and VMware Distributed Resource Scheduler.
This book zooms in on two key components of every VMware based infrastructure. It covers the basic steps needed to create a VMware HA and DRS cluster, and goes on to explain the concepts and mechanisms behind HA and DRS which will enable you to make well educated decisions. You will get the tools to understand and implement e.g. HA admission control policies, DRS resource pools and resource allocation settings and more.

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on Amazon UK



Available in Europe from

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midwestexpAuthor Commented:
Thanks Hanccocka! I had no idea where to begin on searching for what I was looking for and your links answered my question and provided insight to ideas I should keep in mind down the road.
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