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How to disable aggregate freespace reallocation?

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ontap-9
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core
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Applies to

  • ONTAP 9
  • Aggregate Freespace Reallocation (free-space-realloc) / Continuous Segment Cleaning (CSC)

Description

  • Aggregate Freespace Reallocation, sometimes also referred as Continuous Segment Cleaning (CSC), is an aggregate flag:

::> aggr show -fields free-space-realloc
aggregate free-space-realloc
--------- ------------------
aggr0     off

  • When set to anything apart from off, ONTAP will continuesly re-arrage unused blocks within an aggregate in the background
  • By default the flag is set to off and can only get manually enabled.
  • Only in very specific edge cases with HDD based aggregates, this flag is modified to mitigate performance headroom bottlenecks short term. Such bottlenecks are supposed to get mitigated long-term by adding performance headroom via additional drives, etc.
  • Flipping the flag is usually guided by NetApp Customer Support. Refer to Fragmentation and Reallocate for additional details.
  • On AFF platforms or SSD-only aggregates, CSC is never expected to be enabled.

 

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