FreeBSD 12 – ZFS pool enters DEGRADED state after device timeout

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

zpool shows DEGRADED, reducing redundancy and increasing risk.

Environment & Reproduction

Follows transient disk, cabling, or controller timeout events.

Root Cause Analysis

A vdev is faulted or unavailable after I/O timeout handling.

Quick Triage

Identify impacted disk and determine persistent versus transient fault.

Step-by-Step Diagnosis

Map serials, check SMART health, and inspect ZFS event history.

Solution – Primary Fix

Clear transient faults or replace failed media and monitor resilver.

Solution – Alternative Approaches

Address HBA/path instability before reimporting and scrubbing pool.

Verification & Acceptance Criteria

Pool returns ONLINE and scrub ends without new checksum errors.

Rollback Plan

Offline replacement disk and revert to previous validated path.

Prevention & Hardening

Schedule scrubs and proactive SMART monitoring with alerting.

Related Errors & Cross-Refs

Similar symptoms occur from enclosure power instability.

Related tutorial: View the step-by-step tutorial for FreeBSD 12.

View all FreeBSD 12 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

zpool and zfs manuals plus FreeBSD ZFS operations guidance.