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NetApp Knowledgebase

What is the difference between SnapMirror 'normal' and 'low' priority?

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Applies to

  • Clustered Data ONTAP 8.2 and later
  • Clustered Data ONTAP 8.3 and later
  • ONTAP 9.0 and later

Answer

  • SnapMirror normal and low priority are not related to SnapMirror throughput
  • The SnapMirror normal and low priority settings are related to SnapMirror job execution order, pending operations, and job queuing
  • SnapMirror priority is not 'priority,' as in CPU priority
  • SnapMirror priority has no effect on individual jobs when no other jobs are running
  • SnapMirror priority has the most significant effect when there are enough simultaneous jobs to fill up the queue
  • When there are enough simultaneous SnapMirror jobs to fill the queue, it can result in pending jobs
  • Jobs with normal priority will run before jobs with low priority
  • Jobs with low priority will not be run until all of the queued normal priority jobs have run
  • In a scenario where a normal and a low priority job are scheduled to run at the same time, the normal priority job will run first
 

Additional Information

Note: There is a known issue where active SnapMirror transfers will report running at 'low' priority even though the relationship's SnapMirror policy is configured to run at 'normal' priority. The SnapMirrors in this scenario are actually running at 'normal' priority.