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

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Applies to

  • ONTAP 9.4 and later
  • FabricPool

Answer

TR-4598 FabricPool best practices pg 18

Object deletion and defragmentation

FabricPool does not delete blocks from attached object stores. Instead, 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
  • Defragmentation and deletion do not occur until less than the unreclaimed space threshold being referenced by ONTAP is met.
    • When enough (1,024) blocks have zero references, their original 4MB objects are deleted, and a new 4MB object is created.

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.

Additional Information

TR-4598: This percentage, the unreclaimed space threshold, can be customized, but is set to different default levels for different object stores.
  • The default unreclaimed space thresholds are:

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

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