Synology DS918+ NAS Data Recovery

The Synology DS918+ NAS (Network Attached Storage) system is a powerful solution for managing and storing large amounts of data. With its robust features, it is ideal for home offices, small businesses, and even larger enterprises.

Synology DS918+ NAS


However, like any technology, the DS918+ is not immune to errors that can result in data loss. Data recovery is crucial in these situations, but understanding the common errors that occur in Synology NAS devices can help mitigate risks and speed up the recovery process.

1. Disk Failure Errors

One of the most common errors that can affect any NAS device is a disk failure. The DS918+ uses multiple hard drives to store data in various RAID configurations. A single drive failure can trigger warnings such as:

  • Disk degraded: This occurs when one of the drives in the RAID array fails or becomes inaccessible.
  • Disk offline: When the NAS cannot detect a disk at all.
  • Bad sectors: Hard drives with physical issues or damaged areas that cannot read or write data.

These errors are typically the result of physical damage, aging drives, or issues with the connection to the NAS. The best recovery method is to replace the faulty disk with a new one and rebuild the RAID array using Synology’s built-in RAID management tools. If the RAID is in a degraded state, the NAS should still be functional, but data redundancy is at risk.

2. RAID Array Errors

RAID configurations (e.g., RAID 1, RAID 5, or RAID 10) are designed to ensure data redundancy and fault tolerance. However, issues can still arise, particularly in complex RAID setups. Some common RAID-related errors include:

  • RAID rebuilding failure: If a disk in the array fails, the NAS may attempt to rebuild the RAID with a new drive. However, sometimes the rebuilding process fails, resulting in a "RAID degraded" or "RAID failed" error.
  • RAID corruption: Corruption in the RAID metadata can occur for various reasons, including improper shutdowns, system crashes, or hardware faults.
  • RAID array lost after power failure: A sudden power outage or failure can cause inconsistencies in the RAID array, potentially leading to a complete data loss scenario if the system isn't properly restored.

When faced with RAID errors, it’s important to avoid writing new data to the drives. Recovery methods include using Synology’s DiskStation Manager (DSM) to repair the RAID configuration or using third-party RAID recovery tools that support Synology’s RAID structure.

3. File System Corruption

File system corruption can result from abrupt power cuts, improper dismounting of drives, software bugs, or hardware failure. Corruption often results in files or entire directories becoming inaccessible, leading to errors such as:

  • File system not supported: This error may arise if the file system becomes corrupted or mismatched.
  • Volume not mounted: The system might fail to mount a volume, preventing users from accessing stored data.
  • File read/write errors: Files may become corrupted, or the system might fail to read or write to the disk properly.

4. Network Connectivity Issues

Since the DS918+ NAS is designed to be accessed over a network, network connectivity issues can sometimes prevent access to stored data. Common errors include:

  • Cannot access shared folders: This error occurs when the NAS is online but users can’t access specific shared folders or files.
  • Network timeout or slow access: Sometimes, the NAS becomes slow to respond to requests, or the connection times out entirely.
  • IP address conflict: A conflict in the network configuration can prevent the device from being detected on the network.

In these cases, checking the network settings and ensuring the NAS is properly connected to the router and the network is essential. Network issues often can be fixed by resetting network settings or updating firmware. If this does not resolve the problem, advanced troubleshooting such as reviewing logs or resetting the NAS might be necessary.

5. Disk I/O Errors

Input/Output (I/O) errors can occur when the NAS has trouble reading from or writing to the disk, leading to data inaccessibility. These errors are typically associated with failing drives, disk space issues, or corrupted files. Common symptoms include:

  • Disk I/O timeout: The system takes too long to process read/write requests, potentially causing the NAS to freeze or crash.
  • Disk slowdowns: The drives show significantly reduced speeds, possibly due to fragmentation or hardware failure.

To recover from I/O errors, checking for disk health with Synology’s built-in diagnostic tools and running disk repairs through DSM can help resolve minor issues. If the disk is beyond repair, replacing it and restoring data from a backup is often the best solution.

6. Data Loss After Firmware Update

Sometimes, after a DSM firmware update, users may experience unexpected data loss or corruption. This can happen due to various reasons, such as:

  • Incompatible firmware version: Certain updates may be incompatible with specific disk configurations.
  • Incomplete update: An interrupted or failed firmware update can leave the system in an unstable state.
  • File corruption during update: The update process may corrupt files or RAID configurations, leading to inaccessible data.

To avoid this issue, always ensure that you have a backup before performing a firmware update. In case of data loss after an update, rolling back to a previous DSM version might help, though this is not always guaranteed to restore lost data.

7. Accidental Deletion or Overwritten Data

Accidental deletion or overwriting of files can happen in a variety of ways, such as user error or misconfigured settings. If data is lost due to accidental deletion or overwriting, the data may not immediately be erased from the hard drive and could still be recoverable.

Synology DS918+ NAS Data Recovery Case Log

12Feb25:

Synology DS918+ NAS


The Synology DS918+ NAS device experienced a catastrophic failure after being exposed to an electrical surge. The client reported that the system became unresponsive and failed to power on. After troubleshooting and investigation, it was confirmed that the NAS was no longer operational, likely due to the electrical surge damaging internal components.

Initial Assessment:

  1. Power Failure: The NAS failed to power on after the electrical surge.
  2. System Failure: The device showed no signs of life when powered up; no LED indicators were lit, indicating potential power supply damage or motherboard failure.
  3. Drive Health Check: Despite the NAS itself being unresponsive, the drives appeared physically undamaged. There was a concern that the surge could have affected the RAID configuration or data integrity.

Recovery Process:

  1. Drive Removal and Inspection:

    • The hard drives (all four 4TB Western Digital drives) were removed from the Synology DS918+ chassis.
    • Each drive was connected to an external USB drive dock and checked for any signs of physical damage. All drives powered up normally and showed no visible or audible failure (e.g., clicking or abnormal noises).

  2. RAID Reassembly:

    • After confirming that the drives were intact, the next step was to reassemble the RAID configuration. The system had been running a RAID 5 configuration, which includes three active drives and one spare.

  3. Data Extraction:

    • Once the RAID array was successfully rebuilt and operational the next step was to extract the data.
    • The extraction process ran without issue, and all critical data files (documents, images, videos, and backups) were retrieved without corruption or loss.

  4. Final Verification:

    • The extracted data was verified for completeness and integrity.
    • All files were accessible and intact, confirming no data corruption occurred despite the electrical surge's impact on the NAS hardware.