Synology NAS Error Code 24: How to Fix It

Medium 30-90 minutes (active setup); resync itself may take several hours to days depending on array size Medium Severity Verified June 2026
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Error Code
24
Brand
Synology
Product Type
nas
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-90 minutes (active setup); resync itself may take several hours to days depending on array size
Synology NAS Error Code 24 indicates that a RAID resynchronization (resync) process is running unusually slowly on your device. This typically happens after a drive replacement, unexpected shutdown, or system update when DSM begins rebuilding your RAID array to ensure data integrity. While the NAS remains accessible during resync, a slow resync can leave your data unprotected for longer than necessary, making it important to identify and resolve the bottleneck as soon as possible.
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Tools You'll Need

How to Fix Error Code 24

  1. Check Current Resync Status in Storage Manager

    Do NOT power off or reboot your NAS during an active RAID resync. Interrupting the process can lead to data corruption or drive failures.

  2. Reduce System Load During Resync

  3. Increase RAID Resync Speed Limit

    Only use SSH if you are comfortable with command-line interfaces. Entering incorrect commands can affect system stability. Double-check every command before pressing Enter.

  4. Check Drive Health for All Installed Drives

    Back up all critical data to an external drive or cloud storage before replacing any disk or making changes to your RAID configuration.

  5. Check and Improve NAS Ventilation and Temperature

    Power off the NAS before using compressed air to clean internal components. Unplug the power cable before opening the chassis.

  6. Update DSM and Drive Firmware

    Back up your data before performing any firmware or DSM updates. Although rare, updates can occasionally cause unexpected issues.

  7. Verify RAM and Run a Memory Test

    Unplug the NAS power cable before installing or removing RAM modules. Ground yourself using an anti-static wrist strap to prevent static damage.

  8. Make the Speed Limit Change Persistent (Optional)

    Setting resync speed limits too high on older or slower drives can cause drive stress or system instability. Start conservatively and increase gradually.

Parts You May Need

NAS-compatible hard drive
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Compatible DDR3 or DDR4 SO-DIMM RAM module
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Replacement NAS cooling fan
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NAS-compatible hard drive
Check Price on Amazon
Compatible DDR3 or DDR4 SO-DIMM RAM module
Check Price on Amazon
Replacement NAS cooling fan
Check Price on Amazon
NAS-compatible hard drive
Check Price on Amazon
Compatible DDR3 or DDR4 SO-DIMM RAM module
Check Price on Amazon
Replacement NAS cooling fan
Check Price on Amazon
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When to Call a Professional

Contact Synology Support (support.synology.com) or a certified data recovery professional if: (1) S.M.A.R.T. tests show multiple failing drives simultaneously, (2) DSM reports the storage pool as 'Degraded' or 'Crashed' and resync will not start or complete, (3) you hear clicking or grinding noises from any drive bay, (4) the NAS becomes completely inaccessible during resync, or (5) you suspect hardware failure in the NAS controller board. Do not attempt to swap multiple drives at once without professional guidance, as this can cause complete data loss in RAID 5 and RAID 6 arrays.

Frequently Asked Questions

How long does a Synology RAID resync normally take?
Resync time depends heavily on array size and drive speed. A typical RAID 1 array of 4 TB drives may take 4–12 hours, while a RAID 5 or RAID 6 array of 8 TB or larger drives can take 24–72 hours or more. Slow resync (below 10 MB/s) suggests a problem that should be investigated.
Is my data safe while Synology is resyncing?
Your data remains accessible and readable during resync in most RAID types (RAID 1, 5, 6, 10). However, during this window your array is temporarily without full redundancy, meaning if another drive fails before resync completes, you could lose data. Always maintain a backup before and during resync.
Can I use my NAS normally while RAID resync is in progress?
Yes, you can continue using your NAS during resync, but performance may be reduced. For fastest resync completion, it is best to minimize heavy workloads like large file transfers, backup jobs, or media transcoding until the process finishes.
Why did my Synology NAS start resyncing after a power outage?
An unexpected shutdown or power loss can leave the RAID array in an inconsistent state. DSM automatically triggers a resync on the next boot to verify data consistency across all drives and repair any mismatches. This is normal protective behavior and does not necessarily indicate a hardware problem.
Will increasing the RAID resync speed damage my hard drives?
Moderately increasing the resync speed limits via SSH is generally safe for modern NAS-grade hard drives. However, setting limits extremely high on older consumer drives can increase heat and wear. It is recommended to increase speed gradually, monitor drive temperatures in DSM, and keep drives below 50°C during the process.

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