HSX - Data Aging vs DDB Space Reclamation use case

In an HSX environment, Data Ageing and DDB Space Reclamation are complementary but separate processes. Each serves a different purpose in managing and reclaiming storage space, particularly in deduplicated storage pools.

==> Data Aging

Purpose
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Data aging is a logical cleanup process that identifies backup jobs which have exceeded their configured retention period.

How it works
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- Commvault evaluates retention rules and marks eligible jobs as aged.
- A pruning phase then removes job metadata and logical references to those backups.

Impact on disk space
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- In deduplicated storage, data aging does not immediately free disk space.
- Deduplicated blocks may still be shared by other backups, so the physical data remains intact until all references are removed.

Outcome
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- Aged jobs are no longer recoverable.
- Disk usage may remain unchanged immediately after data aging, which is expected behavior in deduplication environments.

==> DDB Space Reclamation

Purpose
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DDB space reclamation is the physical cleanup process that actually frees disk space.

How it works
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- The system scans deduplication containers for unused or unreferenced data blocks.
- Chunks with a high percentage of reclaimable space are rewritten or removed, depending on the reclamation level.

Impact on disk space
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- This process physically deletes unreferenced data blocks.
- Disk space becomes available for new backups only after successful space reclamation.

Outcome
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- A measurable reduction in used disk capacity.
- This is the step where customers typically observe actual space recovery.

==> Why Disk Space Is Reclaimed Only After DDB Space Reclamation

- Data aging removes logical references but does not delete shared deduplicated blocks.
- DDB space reclamation consolidates and removes blocks that are no longer referenced by any job.
- In HSX, reclamation may run automatically when free space thresholds are reached, or it can be initiated manually when immediate space recovery is required.

Thank you very much for this detailed answer!

One last question: I understand that in a HSX environment, data aging jobs will never free up space (physical). Is that correct? There must be always a DDB space reclamation job to complement the logical process made by the data aging job?

regards,

Pedro