Dennis HilkLinux Fix LabDE

Storage & Filesystems

ATA uncorrectable sectors and read errors

Treat repeatable UNC media errors as a data-preservation problem, using drive health and sector evidence before filesystem repair or stress tests.

Editorial source review: Start with the evidenceShare this guide
On this page
  1. Symptoms & scope
  2. Possible causes
  3. Diagnose safely
  4. Evidence-guided next steps
  5. References & review
  6. Related problems

Symptoms & scope

  • The same file or region repeatedly returns a read error.
  • ATA logs include UNC rather than only a link reset.

Relevant environment

ATA disks and SSDs reporting libata errors; SMART support varies with bridges and vendors.

Recognizable messages (synthetic examples)
ata3.00: error: { UNC }

Preserve data and inspect the failing read/LBA; the line does not establish which files were damaged.

Possible causes

These are possible explanations, not a confirmed diagnosis. Several independent faults can coexist.

  • UNC means the device could not recover data after its internal retries; media deterioration or drive firmware may be involved.
  • Filesystem errors can be downstream effects of unreadable sectors, while independent memory or transport faults still need separate evidence.

Diagnose safely

Run one command at a time in the relevant session. Read the explanation first. Uppercase placeholders need your own values; tools and privileges vary by distribution. These commands are displayed here and never executed by the website.

Check 1

Read the kernel log with journal privileges if needed, retaining command, LBA and drive context.

journalctl -k -b --no-pager -n 300

Interpret the result: Repeated UNC at the same LBA is more specific than application EIO. ICRC points to transport corruption and needs a different investigation.

Check 2

Replace /dev/sdX with the whole affected disk; read attributes and existing test/error logs only.

sudo smartctl -x /dev/sdX

Interpret the result: Pending, offline-uncorrectable or growing reallocated counts strengthen the media-fault concern. Vendor attributes and an overall PASS result are not a complete integrity test.

Evidence-guided next steps

Preserve data before repair

If important data is not backed up and UNC recurs, stop avoidable writes. Recover the most valuable readable files or make an error-tolerant rescue image to a different healthy device; seek specialist recovery when the drive becomes mechanically unstable.

Precautions: Do not run destructive bad-block tests or repeatedly scan a failing disk before securing data. A rescue destination must never be the source.

Recovery / rollback: Keep the original powered down after imaging. Recovery work can be repeated on a copy without overwriting the source.

Did this solution help you?

Share this solution#

Replace media when evidence persists

If unreadable LBAs or health counters continue growing on a verified data path, replace the drive and restore from a checked backup or rescued image. Run filesystem verification on the replacement copy before returning it to service.

Precautions: A filesystem repair cannot make damaged media reliable. Confirm restored files independently where checksums or original copies exist.

Recovery / rollback: Retain the original and backup until restoration is verified; do not erase the only remaining copy.

Did this solution help you?

Share this solution#

References & review

This guide was prepared from primary project or distribution sources and reviewed on the date shown. This is an editorial source check, not evidence that a fix was reproduced on your hardware. Diagnostic log examples are synthetic fixtures. Version-dependent details must be checked against your installed release.