How do I perform advanced analysis of disk drop issues?

Applicable Products

• QNAP NAS
• QNAP Expansion Enclosure (if applicable)

Overview

This FAQ is intended for advanced users who want to perform an initial classification and analysis of disk drop issues by reviewing messages and keywords in the Event Log and Kernel Log.

The results described in this FAQ indicate only a Possible Cause or Investigation Direction. They do not represent a confirmed Root Cause.

The same Event Message or Kernel Message can be caused by different factors, such as the disk, disk tray, disk bay, SATA link, backplane, controller, or other system factors. Therefore, a failed component should not be identified based on a single keyword alone.

Important: Kernel Log keywords in this FAQ are intended only to help classify an issue and identify possible investigation directions. A single message or keyword cannot confirm which component has failed. Final Root Cause and hardware failure determination should be based on QNAP Technical Support's analysis of the complete Diagnostic Logs and system status.

Safety: If the RAID is already degraded and another RAID member disk is also abnormal, or if multiple disks in the same RAID group are experiencing issues, protect the data first. Do not remove, swap, or move disks, or perform tests that may increase data risk merely to verify a log-based assumption.

Quick Log Analysis Reference

This table is intended only for quick classification. Do not use a single keyword to conclude that a disk, backplane, or controller has failed. Correlate the message with the Disk/Bay mapping, timestamp, Event Log, surrounding Kernel Log messages, and Disk/Bay isolation test results.

Analysis Principle: Do Not Rely on a Single Keyword

When performing advanced disk drop analysis, check the following in sequence:

1. Confirm the incident time: Identify the exact timestamp of the disk drop and correlate the Event Log and Kernel Log entries around the same time.
2. Identify the disk and bay: Confirm the disk number in the Event Log and correlate it with the ATA/SATA device in the Kernel Log, such as ata10 or ata22. The mapping between an ATA device and a physical disk bay can vary by NAS model. Do not assume that ataX directly corresponds to the same bay number.
3. Identify the error category: Link failed, Unrecoverable error, Command timeout, or Hardware failure.
4. Review surrounding messages: Look for related messages such as Disk disconnected, link reset, read error, UNC, ATA bus error, command timeout, or repeated retry/reset messages.
5. Correlate with isolation results: Determine whether the issue follows the disk, whether different disks show the same issue in the same bay, and whether multiple disks report similar errors at approximately the same time.

# Category 1 — Link failed

Typical Messages

Event Message:

Failed to access the installed drive

Kernel Message / Keyword:

reset failed, giving up

Messages around the same event may also include:

hard resetting link
link is slow to respond
SATA link down
reset failed

How should I interpret these messages?

These messages indicate that the system attempted to establish or recover the SATA link to the disk, but the reset/recovery ultimately failed. The disk may therefore become inaccessible or disconnected.

reset failed, giving up does not by itself mean that the disk has definitely failed. The source cases indicate that the disk should be investigated first; if replacing the disk does not resolve the issue, the SATA controller, signal, or another part of the connection path should also be considered.

Possible Cause / Investigation Direction

• Disk
• Disk connection / SATA link
• Disk Tray / connector
• Disk Bay
• Backplane
• SATA Controller / signal path

Correlation

• The issue follows the disk: The possibility of a disk-related issue increases.
• Different disks show the same Link Failure in the same bay: Increase the investigation priority for the Tray / Bay / Backplane / SATA Controller / Signal Path.
• The disk recovers and then fails again: If repeated reset/recovery messages are followed by reset failed, giving up, analyze the complete communication/link recovery pattern rather than a single reset message.

Category 2 — Unrecoverable error

Typical Messages

Event Messages may include:

Medium error. Run a bad block scan on the drive.
Invalid data found on Host
Medium Error
Unrecovered read error

Kernel Message / Keyword:

UNC

For example:

error: { UNC }

How should I interpret these messages?

UNC, Medium Error, and Unrecovered read error point more directly toward a disk media/read error. In the source case studies, UNC appears together with read errors, Bad Block Scan results, and Disk Health I/O errors.

Possible Cause / Investigation Direction

Disk Media / Bad Sector / Disk

Correlation

Check whether the following are also present:

• SMART abnormality
• Disk Health I/O Error
• Bad Block Scan error
• Medium Error
• Unrecovered read error
• UNC in the Kernel Log

If several of these findings correlate, the possibility of a disk media/read failure increases. However, a single UNC message should still not be used as the final hardware failure determination.

Category 3 — Command timeout

Event Message

This does not specify a fixed Event Message for this category. Analysis therefore relies primarily on the Kernel Log.

Kernel Log Characteristics

The core condition is that the NAS sent a command to the disk but did not receive a response within the expected time. The source guide describes the timeout condition as no response for more than approximately 30 seconds.

In the case study, a timeout may be followed by messages such as:

hard resetting link
link is slow to respond
resetting link
SATA link down
reset failed, giving up

How should I interpret these messages?

A Command timeout indicates that a disk command did not complete within the expected time, but a timeout alone does not confirm that the disk has failed.

The source guide explicitly lists the following possible directions:

• Disk
• SATA Controller failure
• Software bug

During actual troubleshooting, the connection/link path should also be included in the correlation.

Possible Cause / Investigation Direction

Disk / SATA Controller / Connection Path / Software

Correlation

If you see a sequence similar to:

Command timeout
        ↓
hard resetting link
        ↓
link is slow to respond
        ↓
repeated reset/retry
        ↓
reset failed, giving up

analyze the complete sequence instead of only the final message.

• The issue follows the disk: The possibility of a disk-related issue increases.
• Different disks experience timeout in the same Bay / Path: Increase the investigation priority for the Bay / Backplane / SATA Controller / Connection Path.
• Multiple disks experience timeout at the same or similar time: Do not immediately conclude that multiple HDDs failed simultaneously. Investigate the Shared Hardware Path / Controller or other system-level factors.

Category 4 — Hardware failure

Typical Messages

Event Message:

Host: Disk X: Disconnected

Kernel Message / Keyword:

ATA bus error

In the source case study, ATA bus error appears repeatedly for the same ATA device and may be accompanied by messages such as:

failed command
hard resetting link
SATA link up

How should I interpret these messages?

ATA bus error indicates an abnormal condition in the ATA communication path. However:

ATA bus error

does not mean:

Backplane is confirmed faulty

This keyword alone also cannot determine whether the failed component is the disk, disk bay, SATA controller, or another component in the path.

Possible Cause / Investigation Direction

• Disk
• Disk connector / Tray
• Disk Bay
• SATA connection path
• Backplane
• SATA Controller

Correlation

• The same disk continues to report ATA bus errors after being moved to another bay: The possibility of a disk-related issue increases.
• Different disks repeatedly report ATA bus errors in the same bay: The possibility of a Bay / Backplane / SATA Path issue increases.
• Similar ATA bus errors occur across multiple bays: Further investigate the Backplane / SATA Controller / Shared connection path.

# How do I correlate the Event Log and Kernel Log?

For example, if the Event Log only shows:

Host: Disk 5: Disconnected

this tells you only that the system observed Disk 5 as disconnected.

If the Kernel Log around the same timestamp also shows:

ata5: ATA bus error
ata5: hard resetting link

you can further focus the investigation on the ATA communication path associated with that disk. However, this still represents only a Possible Cause / Investigation Direction, not a Confirmed Hardware Failure.

Similarly, if the Event Log reports Medium Error, the Kernel Log reports UNC, and Disk Health / Bad Block Scan results are also abnormal, the possibility of a disk media/read error is higher than when any one of these messages appears alone.

Pattern Correlation Reference

"Higher-priority" in this table refers only to troubleshooting priority and does not confirm the Root Cause.

How should I NOT interpret Kernel Logs?

Do not make direct conclusions such as:

UNC = The disk has definitely failed
reset failed = The disk has definitely failed
ATA bus error = The backplane has definitely failed
Command timeout = The controller has definitely failed

A more appropriate analysis flow is:

Keyword
   ↓
Identify Error Category
   ↓
Review surrounding Kernel Messages
   ↓
Correlate Event Log and Timestamp
   ↓
Identify Disk / Bay / ATA Device
   ↓
Correlate SMART / Disk Health / Bad Block results
   ↓
Correlate Disk/Bay Isolation Test
   ↓
Establish Possible Cause / Investigation Direction
   ↓
QNAP Technical Support performs final analysis

What information should I provide to QNAP Technical Support?

• NAS Model
• QTS/QuTS hero Firmware Version and Build
• RAID Type / RAID Group Status
• Affected Disk Bay / Slot
• Disk Model / Firmware / Serial Number
• Exact timestamp of the disk drop
• Event Log
• Diagnostic Log ZIP
• SMART / Disk Health Result
• Bad Block Scan Result (if performed)
• Disk/Bay Cross Test Result (if performed)
• Kernel Message / Keyword identified during the initial analysis
• Relevant Kernel Log context before and after the keyword

If you have performed an initial analysis, describe the result as:

Possible investigation direction:
Disk / SATA Link / Backplane / Controller / Media Error / etc.

Avoid describing it as:

Confirmed failed component:
...

unless QNAP Technical Support has completed the analysis and confirmed the result.

Summary

The purpose of advanced Disk Drop Log Analysis is not to identify a failed component from a single Kernel Log keyword. Instead, use the Event Log, Kernel Log, and actual troubleshooting results together to progressively narrow the investigation scope.

The four main categories are:

1. Link failed — for example, reset failed, giving up
2. Unrecoverable error — for example, UNC, Medium Error, Unrecovered read error
3. Command timeout — a disk command does not receive a response within the expected time and may be accompanied by repeated link resets
4. Hardware failure — for example, ATA bus error

A keyword provides a Possible Cause / Investigation Direction, not a Confirmed Root Cause.

Final failure analysis and hardware determination should be based on QNAP Technical Support's review of the complete Diagnostic Logs, system status, and isolation test results.

Related Article

• How do I perform initial troubleshooting when a disk drops from a NAS?