QNAP NAS Error Code 18: How to Fix It

Medium 1-2 hours setup time; 8-24 hours for RAID rebuild to complete High Severity Verified June 2026
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Error Code
18
Brand
QNAP
Product Type
nas
Severity
High
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours setup time; 8-24 hours for RAID rebuild to complete
QNAP NAS Error Code 18 indicates that your RAID array is in a degraded state, meaning one or more drives in the array have failed or gone offline, leaving your data at risk. While your NAS may still be accessible, a degraded RAID array offers no fault tolerance — a second drive failure could result in total data loss. It is critical to act quickly: back up your data immediately and follow the steps below to identify the failed drive and restore your RAID array to a healthy state.
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Tools You'll Need

How to Fix Error Code 18

  1. Back Up Your Data Immediately

    Do NOT skip this step. A degraded RAID array (Error Code 18) means you have zero redundancy. Any further failure or power interruption can destroy all data on the array.

  2. Identify the Failed or Degraded Drive

  3. Check the Storage Manager for RAID Status

  4. Run a S.M.A.R.T. Diagnostic Test on All Drives

  5. Replace the Failed Drive (Hot-Swap if Supported)

    Power down the NAS before opening it on non-hot-swap models. Always handle drives by the edges and use an anti-static wrist strap if available. Never force a drive tray — check that the latch is fully released before pulling.

  6. Rebuild the RAID Array

    Do not power off the NAS during the rebuild process. A power interruption mid-rebuild can corrupt the array and cause data loss. Ensure the NAS is connected to a UPS (uninterruptible power supply) if possible.

  7. Verify RAID Health After Rebuild

  8. Enable Proactive Monitoring and Notifications

Parts You May Need

NAS Hard Drive (3.5-inch or 2.5-inch depending on model)
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Drive Tray or Caddy (QNAP compatible)
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Uninterruptible Power Supply (UPS)
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NAS Hard Drive (3.5-inch or 2.5-inch depending on model)
Check Price on Amazon
Drive Tray or Caddy (QNAP compatible)
Check Price on Amazon
Uninterruptible Power Supply (UPS)
Check Price on Amazon
NAS Hard Drive (3.5-inch or 2.5-inch depending on model)
Check Price on Amazon
Drive Tray or Caddy (QNAP compatible)
Check Price on Amazon
Uninterruptible Power Supply (UPS)
Check Price on Amazon
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When to Call a Professional

Contact a professional data recovery service if: (1) multiple drives have failed simultaneously and data is inaccessible, (2) the RAID array will not rebuild after replacing the drive, (3) the NAS itself will not power on or is making unusual clicking or grinding sounds from the drives, (4) you cannot access the QTS interface and critical data has not been backed up. Do not attempt software-level RAID repair tools on failing hardware — this can overwrite data needed for professional recovery. Contact QNAP support directly if your device is under warranty. For critical business data with no backup, engage a professional data recovery lab before attempting any further changes.

Frequently Asked Questions

Will I lose my data when QNAP shows Error Code 18 (RAID degraded)?
Not necessarily — in most cases your data is still accessible and intact when a RAID array is degraded. A degraded state means the array has lost one drive but is still functioning (depending on your RAID type). However, you have no redundancy protection, so a second drive failure at this point will cause total data loss. Back up your data immediately and replace the failed drive as soon as possible.
How long does a QNAP RAID rebuild take after replacing a drive?
RAID rebuild times depend on drive capacity, RAID type, and NAS workload. As a general estimate: a 2TB drive may take 4–10 hours, a 4TB drive can take 8–20 hours, and an 8TB or larger drive may take 24–48 hours or more. You can monitor real-time rebuild progress in Storage & Snapshots in the QTS interface. Avoid heavy NAS usage during the rebuild to speed up the process and reduce the risk of additional errors.
Can I use any hard drive to replace the failed drive in my QNAP NAS?
You should use a drive that is on QNAP's official Hardware Compatibility List (HCL), which can be found at qnap.com/compatibility. The replacement drive must be equal to or larger than the failed drive's capacity. NAS-rated drives (such as those designed for 24/7 operation) are strongly recommended over desktop drives for reliability. Using an incompatible or undersized drive may prevent the RAID from rebuilding correctly.
What is the difference between RAID degraded and RAID failed on a QNAP NAS?
A degraded RAID (Error Code 18) means one drive has failed but the array is still functional and data is accessible — the array is running without full redundancy. A failed RAID means enough drives have failed that the array can no longer function and data may be inaccessible. Degraded is a serious warning state that requires immediate action; a failed RAID typically requires professional data recovery tools and expertise.
Should I enable RAID scrubbing on my QNAP NAS to prevent Error Code 18?
Yes, enabling RAID scrubbing (also called Data Scrubbing) is a best practice that can help detect and correct latent drive errors before they cause a full drive failure. In QTS, go to Storage & Snapshots > Storage > Storage/Snapshots, select your storage pool, click Manage, and look for the Data Scrubbing option. Schedule it to run monthly during off-peak hours. Combining this with regular S.M.A.R.T. tests and email alerts gives you the best early warning system against RAID degradation.

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