NAS owner sets up automated backups, sees reassuring status messages for months, and assumes everything is protected. Then a drive fails, or a file gets accidentally deleted, and they discover the backup hasn’t actually been working — sometimes for weeks, sometimes longer. One user found that a power outage had quietly unmounted his backup drive; another discovered their antivirus had quarantined the sync software. The NAS kept running, the dashboard looked normal, but the safety net was gone.

Key Takeaways:

• NAS backup failures stem from five predictable categories: hardware problems, software or configuration errors, storage running out, network instability, and human mistakes.
• Effective troubleshooting starts with checking logs, disks, network health, backup settings, and running a manual test backup plus a small restore.
• Security software can break backups by blocking or deleting sync services, so you may need to restart the UGREEN sync app, reset its config, or whitelist it in antivirus.
• RAID is not a substitute for backups; even with RAID, you still need verified, working backup jobs to protect against deletion, corruption, and ransomware.

Common Causes of NAS Backup Failures

UGREEN NAS backup failures fall into a handful of predictable categories. Understanding these will help you diagnose problems faster and know where to look first.

Hardware Failures

• Hard drive failure is one of the most common causes. If a drive in your NAS system stops working, the entire backup process may fail. This could happen due to wear and tear, overheating, or power surges.
• Another hardware issue can be related to the NAS device itself, like faulty cables or damaged ports, which disrupt the connection to your backup storage.

Software Failures

• Sometimes, backup software can run into issues, such as bugs or conflicts with updates. An outdated or incompatible version of the software may cause backups to stop running or result in corrupted data.
• Configuration errors are also common. If the backup software is not set up correctly, it might fail to run backups as scheduled, or it may backup the wrong files.
  

Storage Capacity Issues

• Running out of storage space is a frequent cause of backup failures. When the destination drive or NAS volume is full, new backups cannot be written, causing the job to fail partway through or not start at all.
• Backups that grow over time, such as incremental or versioned backups, can gradually consume available space. Without regular monitoring, storage can fill up unexpectedly.

If you find yourself hitting capacity limits often, exploring larger NAS storage options can help ensure your backup system has the room it needs to stay reliable over the long term.

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Network Problems

• Network failures are another major cause of NAS backup issues. Slow network speeds, frequent drops, or poor connectivity can prevent data from transferring smoothly between the NAS device and the backup destination.
• A weak or overloaded network can cause backups to time out, leading to incomplete or failed backup attempts.

Human Error

Human mistakes, such as improper backup settings or mistakenly deleting important files, can also lead to failures. For example, accidentally overwriting existing backups or changing the backup schedule can result in missing or corrupted data. To avoid these pitfalls, it helps to understand **how different backup methods work** and when to use them—our guide on essential NAS backup strategies breaks down the safest approaches so your data stays protected even when human error enters the picture.

How to Troubleshoot NAS Backup Failures

Remain composed if your NAS backup fails. These steps will assist you in identifying the issue and resolving it. They are easy to use and can help you restore your backups.

1. Examine the logs

Sign in to your UGREEN NAS web admin page with an administrator account. Open the Log Center / Logs app from the main app list or Control Panel:

1. In Log Center, switch to the page that shows event / operation / transfer logs, which includes sync and backup activities.
   
   
2. Use the search box and filters to narrow logs by app (e.g., Sync & Backup), task name, time range of the failure, and severity (warning / error). This helps isolate the specific backup job that is failing.
3. Look for entries around the time the backup failed that are tagged as errors or warnings; check the message text for clues such as connectivity problems, permission denied, disk full, or invalid filenames.
4. If logs are sparse or unclear, check for filesystem issues (e.g., very long paths or invalid characters in filenames) or external disk errors.
5. If the UI logs lack sufficient detail, generate a full diagnostic bundle via Support → Contact Us → One-click Generation in the NAS interface and attach it to a support ticket so UGREEN can analyze low-level log files (such as the .slog files under /var/ugreen/log).

2. Examine the Hardware

• Drives: Check the condition of your drives using the NAS tools. You might need a new one if the old one is bad.
• Network connection: Check for any damaged ports or loose cables that may be interfering with the connection between your NAS and the backup storage.
• Power: To ensure consistent power, connect your NAS to a UPS. This prevents abrupt backup stops.
• Temperature: Verify that the NAS isn’t getting too hot. Place it in a cool location with lots of airflow.

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3. Examine the Network

• speed test: Check your network’s performance with a speed test. Backups may fail due to timeouts caused by slow speeds.
• Firewall: Check for obstructions caused by the firewall. To allow the backup to pass through, you may need to adjust it.

4. Examine the Backup Configuration

• Folders: Verify again that the correct folders are being backed up.
• Space: Examine the drive to ensure that there is adequate space for the backup. If space is limited, make room.

5. Examine the backup

• Manual Backup: Check to see if the backup was successful by running it yourself.

Try restoring a small file as a restore test. Your backup is probably good if it functions.

6. Examine Security Software

The synchronization backup program may be mistakenly identified as a virus or malware by antivirus software, leading to its blocking or deletion, which prevents the service from starting.

How to Fix “Service Error” for Local Sync/Backup Tasks

Open the UGREEN NAS client and go to the [App Center], Click on “Sync & Backup” to enter the application details page. Select “Disable” in the upper left corner, then click “Enable” to restart the sync service.

Windows Computer Troubleshooting

Right-click the UGREEN NAS icon in the Windows system tray, select Exit, then restart the UGREEN NAS client. Press Ctrl + Shift + Esc to open Task Manager, then search for syncSpace to see if the program is running.

If it is not running:

• Check the Recycle Bin and your antivirus software to ensure that the syncSpace program has not been mistakenly deleted.
• Verify whether the syncspace_pro.exe file exists in the UGREEN NAS installation directory (path: C:\Program Files\UGREEN NAS\resources\public\win32\syncspace).

If the program is running:

1. Exit the UGREEN NAS client.
2. Using Windows File Explorer, navigate to the folder: Application Support/com.ugreen.desktop/UGREEN_Nas_Pro/apps/syncSpace and open it.
3. Inside the syncSpace folder, you will see multiple folders named after device serial numbers (SN), such as 1000ECxxxxxxxxx.
4. Locate the folder corresponding to your device and open it, then delete the .config folder inside.
5. After deleting, reopen the UGREEN NAS client and check if the issue is resolved.

Mac Computer Troubleshooting

1. Exit the UGREEN NAS client.
2. Hold down the Option key, click the [Go] menu at the top-left corner of the screen, and select Library.
3. Navigate to Application Support/com.ugreen.desktop/UGREEN_Nas_Pro/apps/syncSpace and open this folder.
4. Inside the syncSpace folder, you will see multiple folders named after device serial numbers (SN), such as 1000ECxxxxxxxxx.
5. Locate the folder corresponding to your device and open it, then delete the .config folder inside.
6. After deletion, reopen the UGREEN NAS client and check if the issue is resolved.

Quick Steps Table

FAQ About NAS Backup

Why does my NAS backup keep failing at the same percentage?

This usually indicates a problematic file at that point in the backup. Common culprits include corrupted files, files with very long names, or files locked by another application. Check your backup logs to identify which specific file is causing the failure, then address it directly.

Should I use RAID instead of backups?

No — RAID and backups serve different purposes. RAID protects against drive failure and keeps your system running, but it won’t protect you from accidental deletion, ransomware, or file corruption. Always maintain separate backups, even with a RAID configuration.

If you want a clearer understanding of how each RAID level behaves—and why it can’t replace proper backups—our guide on choosing the best RAID setup breaks down the strengths and limits of common RAID options in everyday NAS use.

What’s the difference between incremental and full backups, and which should I use?

A full backup copies everything each time, while an incremental backup only copies files that have changed since the last backup. Incremental backups are faster and use less storage, but full backups are simpler to restore from. Many users combine both: periodic full backups with daily incremental backups in between.For a deeper look at how to structure an efficient long-term backup routine, including when to use each method, see our guide on choosing the right NAS backup strategy.

My backup software says it completed, but some files are missing. What happened?

This can occur when files are excluded by filter rules, skipped due to permission errors, or locked during the backup window. Review your backup settings for exclusion filters, check logs for skipped files, and ensure backups run when files are not in active use.