ZFS Pool Degraded State on FreeBSD 15

📖 ~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 status reports DEGRADED with checksum or read errors.

Environment & Reproduction

Failing disk, loose cabling, controller errors, or unrecoverable media sectors.

Root Cause Analysis

Use zpool status -v and smartctl checks to identify the exact member device.

Quick Triage

If redundancy exists, replace the failed member promptly and keep backups current.

Step-by-Step Diagnosis

Run zpool status -v and zpool events -f to monitor real-time error activity.

Solution – Primary Fix

Inspect /var/log/messages for CAM or disk transport errors tied to the same device.

Solution – Alternative Approaches

Offline bad disk if needed, replace hardware, then zpool replace and wait for resilver completion.

Verification & Acceptance Criteria

Confirm pool returns ONLINE and no new read/write/checksum errors are accumulating.

Rollback Plan

Schedule zpool scrub and SMART monitoring with alerting on pre-failure metrics.

Prevention & Hardening

If replacement fails, restore critical datasets from snapshots or external backup.

Related Errors & Cross-Refs

Escalate when multiple disks fail or controller faults risk full pool loss.

Related tutorial: View the step-by-step tutorial for freebsd-15.

View all freebsd-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

zpool status -v; zpool replace ; zpool scrub ; zpool events -f