Synology NAS Error Code 15: How to Fix It
Medium 30 minutes to several hours depending on RAID rebuild time High Severity
Verified June 2026
- Error Code
- 15
- Brand
- Synology
- Product Type
- nas
- Severity
- High
- DIY Difficulty
- Medium
- Estimated Fix Time
- 30 minutes to several hours depending on RAID rebuild time
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Tools You'll Need
- Web browser (to access DSM interface)
- Phillips screwdriver (to remove drive trays on some NAS models)
- Anti-static wrist strap
- External USB hard drive or network storage (for emergency backup)
- Replacement SATA hard drive compatible with your Synology NAS model
- Flashlight (to inspect drive bays and connectors)
How to Fix Error Code 15
-
Check DSM Notifications and Storage Manager
Do not shut down the NAS until you have assessed the current health status and ideally backed up critical data if it is still accessible. -
Run an Immediate Data Backup
Never skip this step. Attempting repairs on a degraded or failing drive without a backup first risks permanent, unrecoverable data loss. -
Run S.M.A.R.T. Test on the Affected Drive
-
Reseat the Drive Physically
Always perform a clean DSM shutdown before physically removing drives to avoid file system corruption. Handle drives with care — avoid static discharge by grounding yourself first. -
Run a Storage Pool Scrub or Repair
Do not interrupt a scrub or repair operation once started. Interrupting the process can worsen data integrity issues. -
Check DSM and Firmware for Updates
-
Replace the Failing Drive if Confirmed Bad
Only replace drives listed on Synology's official compatibility list for your model to avoid further errors. Do not use a replacement drive smaller than the original drive's capacity. -
Inspect the Drive Tray and NAS Enclosure
If you suspect a backplane or enclosure issue, contact Synology support rather than attempting to repair internal PCB components yourself.
Parts You May Need
Compatible SATA hard drive
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Drive tray or caddy
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External USB hard drive or NAS-compatible external storage
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Compatible SATA hard drive
Check Price on Amazon
Drive tray or caddy
Check Price on Amazon
External USB hard drive or NAS-compatible external storage
Check Price on Amazon
Compatible SATA hard drive
Check Price on Amazon
Drive tray or caddy
Check Price on Amazon
External USB hard drive or NAS-compatible external storage
Check Price on Amazon
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When to Call a Professional
Contact a professional data recovery service if your storage pool is in a crashed or non-redundant state (Basic/JBOD) and you cannot access your data, or if multiple drives have failed simultaneously. If the error persists after replacing the drive and running a repair, and your NAS is under warranty, contact Synology technical support directly. A professional IT technician should also be engaged if your NAS stores mission-critical business data that cannot tolerate any downtime or risk during DIY repair attempts.Frequently Asked Questions
What does Synology Error Code 15 mean?
Synology DSM Error Code 15 is a disk read error, meaning the NAS operating system was unable to successfully read data from one or more hard drives. It typically indicates a failing hard drive, a loose SATA connection, file system corruption, or a degraded storage pool. It is a high-severity error that should be addressed immediately to prevent data loss.
Will I lose my data if I get Synology Error Code 15?
Not necessarily, but you are at significant risk. If your NAS uses a redundant RAID configuration like RAID 1, RAID 5, or SHR, you may be protected as long as only one drive is affected — the array can often be rebuilt. However, if you are using a non-redundant setup or multiple drives have failed, data loss is a real possibility. Back up your data immediately before attempting any repairs.
Can I hot-swap a failing drive to fix Error Code 15?
Yes, Synology NAS units generally support hot-swapping drives in redundant RAID configurations (RAID 1, RAID 5, RAID 6, SHR, SHR-2). You can remove the failed drive and insert a compatible replacement without powering down the NAS, then use Storage Manager to initiate a pool repair. However, if your NAS uses a Basic or JBOD configuration, you should not hot-swap without first powering down and ensuring you have a complete backup.
How long does it take to rebuild a RAID after fixing Error Code 15?
RAID rebuild times depend on the total drive capacity and the speed of your drives. A 2TB drive may rebuild in 4–8 hours, while a 10TB or larger drive can take 24 hours or more. During this time, your NAS remains accessible but performance may be reduced. Avoid powering off the NAS or adding heavy workloads during the rebuild to reduce the risk of a second drive failure.
How can I prevent Synology Error Code 15 from happening again?
To reduce the risk of future disk read errors, schedule regular S.M.A.R.T. tests and storage pool scrubs through DSM's built-in scheduler. Keep DSM firmware up to date, ensure your NAS has adequate ventilation to prevent drive overheating, use drives from Synology's official compatibility list, and maintain a regular backup strategy using Hyper Backup or another solution. Consider upgrading to a redundant RAID configuration if you are currently using a Basic or JBOD setup.