Why is max dop recommended value related to the number of NUMA nodes?



  • Sql server recommendation is to decide max dop based on number of processors in a single Numa node.

    Given a system with 4 Numa nodes, each having 6 processors, the max dop recommended hence would be 6.

    Why is max dop related the number of NUMA nodes?



  • Why is max dop related the number of NUMA nodes?

    Accessing memory on the NUMA node that the threads are running on is somewhat faster than accessing memory on other NUMA nodes. And parallel plans will run on a single NUMA node if it has enough cores (aka schedulers).

    So it's a nice compromise to enable parallel queries while limiting their system-wide impact and promoting efficient query execution.

    It's not at all mandatory, however, as you may have jobs that need MAXDOP 0. Also remember you can override the server MAXDOP at the database, workload group, or query level.




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