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

Last modified date: 2026-10-02

Applicable Products

QNAP NAS
QNAP Expansion Enclosure (if applicable)

Overview

If an HDD or SSD in a QNAP NAS suddenly becomes undetected, shows as disconnected, or the system reports messages such as Disk I/O Error, Disk Plugged Out, or RAID Degraded, follow this FAQ to perform initial troubleshooting.

A disk drop does not necessarily mean that the HDD/SSD itself has
failed. The issue may also be related to the disk tray, disk bay, backplane, SATA/SAS/NVMe connection, controller/HBA, expansion enclosure, power, or drive compatibility/firmware.

Important: If the RAID is already degraded and another RAID member
disk is also showing an abnormal status, or if multiple disks in the
same RAID group are experiencing issues, stop disk swapping, RAID
rebuilding, and high-I/O disk tests. Protect your data first and
contact QNAP Support.

Quick Troubleshooting Reference

Observation	Possible Cause / Investigation Direction
The same disk has the issue in different bays	Disk
The manufacturer's diagnostic tool also reports an error	Disk
SMART / Bad Block Test reports an error	Disk
Different disks have the same issue in the same bay	Tray / Bay / Backplane
The issue no longer occurs after replacing the tray	Disk Tray
The disk reappears after a disk drop and SMART is normal	Tray / Connection / I/O Path
Disks in different bays experience disk drops over time	Do not assume individual HDD failures; investigate the Tray / Shared Hardware Path
Multiple disks drop at the same time	Backplane / Controller / Power / Expansion Path
Multiple disks in an expansion enclosure disappear at the same time	Expansion Enclosure / Connection / Power / Shared Path
A disk drop occurs together with a system crash or other system error	Contact QNAP Support for further System / Kernel / Hardware analysis

The table above provides initial troubleshooting directions only and should not be used by itself to make a final determination of the failed
component.

Solution

1. Check the RAID and data status

Open Storage & Snapshots and check the status of the storage pool, RAID group, other member disks, and data accessibility.

If two or more disks in the same RAID group are abnormal, the storage pool is inactive, or the data is inaccessible, stop further testing.

2. Record the issue information

Before rebooting the NAS or removing the disk, record:

NAS model
QTS/QuTS hero firmware version and build
RAID type and storage pool / RAID group
Affected disk bay / slot
Disk model, capacity, firmware, and serial number
Exact date and time when the disk drop occurred
Whether the disk recovered automatically
Whether any other disks experienced the same issue at the same or a similar time
What task the NAS was performing when the issue occurred

Take screenshots of Storage & Snapshots > Disks/VJBOD and the RAID/storage pool status.

3. Check disk compatibility

Verify that the HDD/SSD is listed on the QNAP Compatibility List and record the disk firmware version. Do not update the drive firmware solely as a troubleshooting step for a disk drop.

4. Check the event log and disk health

In QuLog Center > System Event Log, check for events around the time of the issue, such as Disk disconnected, Disk I/O error, RAID degraded, SMART warning, or Expansion enclosure disconnected.

In Storage & Snapshots > Disks/VJBOD, check the disk health, SMART information, temperature, and Reallocated/Pending/Uncorrectable Sector values.

5. Collect diagnostic logs before further troubleshooting

If the NAS GUI is still accessible, go to:

Helpdesk > Diagnostic Tool > Download Logs

Download the diagnostic log ZIP file before considering a reboot. An accurate incident timestamp can help QNAP Support correlate the issue with kernel and storage-related messages.

6. Run disk tests only when the RAID and data are safe

If the RAID is stable, no other member disk is abnormal, and important data has been backed up, consider running:

Complete SMART Test
Scan for bad blocks

If the RAID is degraded or another member disk is abnormal, do not run long-duration disk tests.

7. Perform a disk/bay isolation test if necessary

If the disk can be safely removed:

Move the suspected disk to another known-good bay and check whether the problem follows the disk.
If necessary, connect the disk to a PC or use an appropriate SATA-to-USB adapter, and test it with the disk manufacturer's diagnostic tool.

If the problem follows the disk → Investigate the disk first.
If different disks have the same problem in the same bay → Investigate the disk tray, bay, backplane, or I/O path.

Do not randomly swap RAID member disks. Before moving a disk, record
its serial number, original bay/slot, and RAID group. If you are
unsure whether the disk can be safely moved, stop and contact QNAP
Support.

What NOT to Do

Do not reboot immediately before collecting diagnostic logs.
Do not repeatedly remove and reinsert the same disk.
Do not randomly swap RAID member disks.
Do not force a RAID rebuild when another member disk is already abnormal.
Do not run long-duration disk tests on a degraded RAID when doing so could put the data at risk.
Do not assume that the HDD/SSD has failed before confirming the cause.
Do not change multiple variables, such as the disk, tray, and firmware, at the same time.

When should I stop troubleshooting?

Stop further testing and contact QNAP Support if multiple disks in the RAID are abnormal, the storage pool is inactive, data is inaccessible, multiple disks experience disk drops or I/O errors at the same time, the RAID rebuild repeatedly fails, a disk repeatedly disconnects and reconnects, the NAS crashes or restarts unexpectedly, or important data does not have a verified backup.

What should I provide when contacting QNAP Support?

NAS model / firmware version and build
RAID type / RAID group status
Disk bay, model, firmware, and serial number
Exact timestamp of the disk drop
Whether the disk recovered automatically and whether other disks
experienced the issue at the same time
Storage & Snapshots screenshots
SMART / Disk Health results
Complete SMART / Bad Block Scan results (if performed)
System Event Log
Diagnostic Log ZIP file
Disk/Bay Cross Test and manufacturer diagnostic test results (if performed)