📖 ~1 min read
Table of contents
Symptom & Impact
RAID operates in degraded mode, increasing risk of data loss and performance drops.
Environment & Reproduction
Appears after disk timeouts, UUID mismatch, or delayed member discovery.
Root Cause Analysis
One or more member devices fail assembly or are marked faulty during boot.
Quick Triage
Identify missing/failed member and read kernel assembly messages.
Step-by-Step Diagnosis
Validate array metadata and compare expected UUID across members.
Solution – Primary Fix
Re-add healthy member and monitor rebuild progress.
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Solution – Alternative Approaches
Replace failed disk and recreate matching partition before adding.
Verification & Acceptance Criteria
Array returns to clean state with all members active.
Rollback Plan
Stop attempted re-add and restore prior backup if rebuild fails.
Prevention & Hardening
Enable mdadm monitoring and alerting for degraded events.
Related Errors & Cross-Refs
Related to SATA cabling faults and controller timeout resets.
Related tutorial: View the step-by-step tutorial for Debian 13.
View all Debian 13 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Debian mdadm administration and RAID recovery documentation.
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