- ONTAP 9.4 and later
- Fabric Pool
- 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.
- 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
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.