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How many VMs should I have ?

    Question

  • I am having a physical server at my head office. It is having 8 cores and 32 GB of RAM.

    I planned to have following 9 VMs

    1. DC
    2. ADRMS server
    3. Sql Server
    4. Exchange Server
    5. MOSS
    6. System Center server (contains system center products)
    7. ADFS Server
    8. Stirling Server
    9. OCS Server

    My question is "Should I have 9 VMs or 8 VMs because my processor is 8 core so each vm will take one core if I choose 8 VM"

    If your suggestion is 8 then which two should I merge ?

    -Master
    Monday, May 18, 2009 4:05 PM

Answers

  • One VM does not consume one core or one processor.  The physical cores and processors are subdivided into virtual CPUs.

    In your proposed installation your contraints will be:  1 - RAM, 2 - physical disk I/O
    You have more than enough processor.


    Brian Ehlert (hopefully you have found this useful)
    Monday, May 18, 2009 4:40 PM
    Moderator

All replies

  • One VM does not consume one core or one processor.  The physical cores and processors are subdivided into virtual CPUs.

    In your proposed installation your contraints will be:  1 - RAM, 2 - physical disk I/O
    You have more than enough processor.


    Brian Ehlert (hopefully you have found this useful)
    Monday, May 18, 2009 4:40 PM
    Moderator
  • Very open question to answer from such little data.  Brian's post explains the technical issue of multiple CPU's which you refer.  You'll need to look into things like:

    How many users do I need to support?
    How much NIC and Disk traffic will those users generate?
    How many Windows licenses do I have? (Standard, Enterprise and Data Center all have different VM licensing terms)

    Shane Cribbs

    Monday, May 18, 2009 4:48 PM
  • Four VM's per logical core.  For ex:  Dual Quad-core has 8 logical procs, times 4 vm's, can host ~32 vm's, but can be over-subscribed. 

    http://blogs.msdn.com/virtual_pc_guy/archive/2008/07/18/processor-topology-inside-of-hyper-v-virtual-machines.aspx


    rmouton

    Monday, May 18, 2009 9:39 PM
  • Hi all,


    one more question. As we know there is "NLB" for load balancing between Servers.

    If I am using Exchange in Hyper-V Environment then do i need to use "NLB" becasue there is enough RAM(or other hardwares) available for utilization.

    In other words "Is is right/good to distribute the load of a single VM into two VMs ? Will it give performance acceleration.?"
    -Master
    Tuesday, May 19, 2009 5:00 AM
  • NLB between VMs is more than load distribution.  You can also consider it failover.  If one dies, you get the second.

    But, your question is good.  Considering all of the additional flexability, recoverability, HA, etc. that you get with a VM, do you need to have failover and load balancing at the VM OS level?

    IMHO, it is a risk tolerance decision.  What is the SLA?  what is the expectation?
    If Exchange is expected to be 24/7/365 - then I would most definately have my implementation reflect that.

    Don't forget that the NLB config also gives you the opportunity to reboot, patch, and do any maintenance on one while the other is servicing requests.


    Brian Ehlert (hopefully you have found this useful)
    Tuesday, May 19, 2009 3:26 PM
    Moderator
  • Awesome answer.

    Thanks Brian; really good one. You saved my time from reading several articles. Your last post is really an essence.
    -Master
    Tuesday, May 19, 2009 4:41 PM