Cannot backup files to an external SSD

Hello,

Thank you for posting your question on our forum.

If Windows Backup that used to work suddenly starts failing, it’s usually caused by a permissions or indexing change, a corrupted system image process, or a problem with Volume Shadow Copy.

Here are steps you can folllow to resolve the issue:

1) Check the Error Details

Even though the message says “backup didn’t complete,” there’s almost always a more specific error code or message.

- Go to Control Panel → System and Security → Backup and Restore.
- Click View details or View backup logs.
- Note any error codes (for example, 0x81000037, 0x80780119, etc.).

2) Run CHKDSK on Both Drives

File system errors on either drive can break the backup chain.

- Open Command Prompt as Administrator and run:

chkdsk C: /f
chkdsk E: /f

(Replace E: with your external SSD’s drive letter.)
If CHKDSK schedules a run for the next restart, allow it.

3) Reset the Windows Backup Catalog

Sometimes the backup catalog itself becomes corrupted.- Open Control Panel → Backup and Restore.
- Click Manage space → View backups → Delete old backup sets.
- Then click Change settings and set up the backup again from scratch.
This clears stale metadata that can cause failures.

4) Check Volume Shadow Copy Service (VSS)

Windows Backup depends on VSS. If VSS fails, the whole backup fails.

- Press Win + R, type services.msc, and press Enter.
- Find Volume Shadow Copy, set Startup type: Manual. Right-click → Start.
- Ensure Windows Backup and Block Level Backup Engine Service are set to Manual or Automatic and can be started.

You can also test VSS manually by using vssadmin list writers (enter in command prompt as admin). Look for entries showing “failed” or “timed out.

5) Check External Drive Path and Permissions

If your backup drive letter changed or permissions broke, Windows may fail to finalize the backup.

- Confirm the drive letter hasn’t changed from what the scheduled task expects.
- In File Explorer, right-click the drive → Properties → Security tab → ensure your account (and SYSTEM) have Full Control.

6) Try Creating a New System Image Separately

If the failure occurs at the image creation stage, isolate it:- In Control Panel → Backup and Restore → Create a system image.
- Select your external SSD and see if that completes.
- If the system image fails but file backup succeeds, it’s a VSS or shadow storage issue.

7) Clear Old Shadow Copies

- Run Command Prompt as Administrator and execute vssadmin delete shadows /all

This deletes leftover shadow copies that sometimes block new ones from being created.

8) Alternative Backup Options (Non-Cloud)

If you can’t get the built-in tool stable again, consider switching to a modern, free backup utility that doesn’t depend on Windows’ legacy backup service.

Here are two excellent options:

Macrium Reflect Free - reliable disk image and file-based backup, supports scheduling, external drives, and differential backups.

AOMEI Backupper Standard – similar to Macrium, simpler interface, also supports external SSDs.

Both are local, not cloud, and much more robust than Windows’ aging backup system.

9) For deeper troubleshooting, check Event Viewer:

Open Event Viewer → Applications and Services Logs → Microsoft → Windows → Backup → Operational.
Look for recent “Error” entries - they often explain which phase failed.

If you need further assistance, please don't hesitate to contact us!