FreeBSD 14 – 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 status shows DEGRADED and resilver risk increases if additional disk faults occur.

Environment & Reproduction

Usually follows transient SAS/SATA errors, cable issues, or controller resets.

zpool status -xv
zpool list
dmesg -a | egrep -i 'ahci|nvme|cam|timeout|error' | tail -n 80

Root Cause Analysis

I/O timeout marks one vdev as faulted or unavailable, degrading redundancy.

Quick Triage

Identify exact device and confirm if fault is persistent or transient.

zpool status
camcontrol devlist
glabel status

Step-by-Step Diagnosis

Cross-check serial mapping and SMART health for impacted device.

smartctl -a /dev/
geom disk list 
zdb -l /dev/

Solution – Primary Fix

Replace or online recovered device, then monitor resilver completion.

zpool clear 
zpool online  
# or replace failed media
zpool replace   

Solution – Alternative Approaches

If pathing issue, reseat cable or HBA lane and re-import pool safely.

zpool export 
zpool import -f 
zpool scrub 

Verification & Acceptance Criteria

Pool returns ONLINE and scrub completes with zero checksum/read/write errors.

zpool status -xv
zpool events -v | tail -n 80

Rollback Plan

If replacement introduces issues, offline new disk and restore previous proven path.

zpool offline  
zpool online  

Prevention & Hardening

Run periodic scrubs and proactive SMART alerting to detect latent failures early.

sysrc zfs_enable=YES
zpool set autoreplace=on 
zpool scrub 

Related Errors & Cross-Refs

Similar symptoms can come from enclosure power events and unstable HBAs.

Related tutorial: View the step-by-step tutorial for FreeBSD 14.

View all FreeBSD 14 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

zpool and zfs manuals, FreeBSD ZFS operational guidance, and SMART tooling docs.