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What does ONTAP do with available IDLE cycles on the storage controller?

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ontap-9
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perf
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Applies to

  • ONTAP 9
  • Clustered Data ONTAP 8
  • Data ONTAP 7-Mode

Answer

ONTAP is opportunistic, when there are available IDLE CPU cycles (IDLE time), instead of wasting the IDLE time, ONTAP can and will use as much of the available time as possible to run background and scheduled tasks such as:

  • WAFL scanners
  • Disk scrubs
  • Media scrubs
  • Scheduled background Deduplication
  • Sparse directory pruning
  • Snapmiror replication
  • WAFL file deletion/clean up operations and so on

ONTAP might show increased activity on CPU and/or disk while there is little to no activity from clients.

Additional Information

  • In Unified Manager and other monitoring or diagnostic tools, Node layer and other layers such as SVM, D-blade or Aggregate layers can report increased latency even though there is little to no work from the clients/users/applications on the storage system.
  • This increased latency is expected since the storage system becomes busy with work it is doing in the background (by design), when the work is complete, utilization and latency can drop back to the normal levels.  This is by design.
  • If the background tasks are still running when clients/users/applications send work to the storage system, the background tasks will yield to that work, giving the inbound work a higher priority.
  • ONTAP will continue background work at a higher priority once IDLE cycles become available again.
 
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