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NUMA Spanning RRS feed

  • Question

  • I've have an SQL server that is about to be virtualised and therefore thinking about disabling NUMA spanning on the hyper-v host. Question is, I've checked via perfmon how much memory is available on each node and it around 75-25 split.  I'd like to know how this split between the 2 NUMA nodes is determined. 

    Thanks in advance

    Thursday, January 19, 2012 3:34 AM

Answers

  • Virtual machines are placed on NUMA nodes by looking at a combination of their virtual processor usage / needs and their memory usage / needs.  Our goal is always to keep the memory and processors for any given virtual machine on a single NUMA node.


    Cheers,
    Benjamin Armstrong
    ============================
    Windows Virtualization
    Senior Lead Program Manager

    This posting is provided AS IS with no warranties, and confers no rights. You assume all risk for your use.
    • Proposed as answer by Vincent Hu Thursday, January 19, 2012 6:00 AM
    • Marked as answer by B77 Thursday, January 19, 2012 8:47 PM
    Thursday, January 19, 2012 4:47 AM

All replies

  • Virtual machines are placed on NUMA nodes by looking at a combination of their virtual processor usage / needs and their memory usage / needs.  Our goal is always to keep the memory and processors for any given virtual machine on a single NUMA node.


    Cheers,
    Benjamin Armstrong
    ============================
    Windows Virtualization
    Senior Lead Program Manager

    This posting is provided AS IS with no warranties, and confers no rights. You assume all risk for your use.
    • Proposed as answer by Vincent Hu Thursday, January 19, 2012 6:00 AM
    • Marked as answer by B77 Thursday, January 19, 2012 8:47 PM
    Thursday, January 19, 2012 4:47 AM
  • Thanks Ben, so to ensure the best performance for the SQL server, is it best practice that I disable NUMA spanning.
    • Edited by B77 Thursday, January 19, 2012 7:31 PM
    Thursday, January 19, 2012 7:31 PM
  • Definitely.  NUMA spanning disabled == best performance.  NUMA spanning enabled == highest number of virtual machines running on a system.
    Cheers,
    Benjamin Armstrong
    ============================
    Windows Virtualization
    Senior Lead Program Manager

    This posting is provided AS IS with no warranties, and confers no rights. You assume all risk for your use.
    Thursday, January 19, 2012 8:32 PM
  • Awesome, cheers Ben.
    Thursday, January 19, 2012 8:47 PM
  • Hi Ben,

    I want to clarify something:

    You sad that VM is placed in single NUMA node when possible, but if this is not possible it will use 2. So enabling NUMA nodes will let us run more VMs with best  performances when possible, less performances when needed.

     

    Is that true ?

    Thanks


    Regards, Samir Farhat Infrastructure Consultant
    Friday, January 20, 2012 6:32 PM