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In what scenario are objects removed or deleted from the cloud tier

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ontap-9
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Applies to

  • ONTAP 9.4 and later
  • Fabric Pool

Answer

  • FabricPool defragments objects based on the percentage of used blocks in the object.
  • Defragmentation reclaims space that is used by blocks that have been deleted or that are no longer being referenced by ONTAP's local tier.
  • Note:
    • Consider reducing unreclaimed space thresholds when you use Infrequent Access/Cool pricing schemes.
    • To change the default thresholds, use the following command:
      storage aggregate object-store modify –aggregate <name> -object-store-name <name> –unreclaimed-space-threshold <%>
      • Advanced privilege levels are required to modify unreclaimed-space-threshold.
      • The default unreclaimed space thresholds are:

• 14% IBM Cloud Object Storage
• 15% Microsoft Azure Blob Storage
• 20% Amazon S3
• 40% StorageGRID

Additional Information

tr-4598 FabricPool best practices 9.9.1

Object deletion and defragmentation

  • FabricPool does not delete blocks from attached object stores.
    • Instead, FabricPool deletes entire objects after a certain percentage of the blocks in the object are no longer referenced by ONTAP.
  • For example, there are 1,024 4KB blocks in a 4MB object tiered to Amazon S3.
    • Defragmentation and deletion do not occur until less than 205 4KB blocks (20% of 1,024) are being referenced by ONTAP.
    • When enough (1,024) blocks have zero references, their original 4MB objects are deleted, and a new object is created.
  • This percentage, the unreclaimed space threshold, can be customized, but is set to different default levels for different object stores.
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