Problem
A backup repository's deduplication index becomes inconsistent after an abrupt shutdown, making restores slower or incomplete despite the underlying chunks still existing.
Solution
Root Cause / Diagnostic:
Deduplication engines (e.g., Borg, Restic, or ZFS deduplication) maintain complex hash indexes mapping chunk hashes to physical blocks. An abrupt power cut or dirty shutdown during index compaction can corrupt index tables; the physical data chunks remain on disk, but the engine cannot locate them, stalling or failing restore jobs.
Actionable Fix:
1. Dedicated UPS & Clean Shutdown Scripts: Ensure the backup host has clean shutdown automation configured via UPS signaling to prevent sudden power loss during index transactions.
2. Index Check & Repair Routine: Execute repository repair commands (e.g., `restic check --read-data-subset=5%` or `borg check --repair`) on a scheduled bi-weekly maintenance schedule.
3. Secondary Non-Deduplicated Backup Copy: Maintain a secondary standard file-level or snapshot-based backup that does not rely on complex deduplication databases for emergency recovery.
Pro Tip:
Deduplication saves massive disk space, but an interrupted write can corrupt the master index; always run automated bi-weekly repository checks to verify your backup index remains healthy.
Deduplication engines (e.g., Borg, Restic, or ZFS deduplication) maintain complex hash indexes mapping chunk hashes to physical blocks. An abrupt power cut or dirty shutdown during index compaction can corrupt index tables; the physical data chunks remain on disk, but the engine cannot locate them, stalling or failing restore jobs.
Actionable Fix:
1. Dedicated UPS & Clean Shutdown Scripts: Ensure the backup host has clean shutdown automation configured via UPS signaling to prevent sudden power loss during index transactions.
2. Index Check & Repair Routine: Execute repository repair commands (e.g., `restic check --read-data-subset=5%` or `borg check --repair`) on a scheduled bi-weekly maintenance schedule.
3. Secondary Non-Deduplicated Backup Copy: Maintain a secondary standard file-level or snapshot-based backup that does not rely on complex deduplication databases for emergency recovery.
Pro Tip:
Deduplication saves massive disk space, but an interrupted write can corrupt the master index; always run automated bi-weekly repository checks to verify your backup index remains healthy.