Backup Snapshot Consistency Violation: How to Fix VSS Errors

When This Error Hits

You're running a backup — maybe Windows Backup, maybe a third-party tool like Acronis or Veeam — and it stops with "The backup snapshot could not be created" or something like "Volume Shadow Copy Service (VSS) reported a consistency violation." The error code is often 0x81000101 or VSS_E_WRITERERROR_RETRYABLE. This usually happens right after a Windows update that didn't finish cleanly, or when your system drive is down to under 5GB free space. I've seen it most on Windows 10 22H2 and Windows 11 23H2 after a failed cumulative update.

Root Cause: VSS Snapshot Broke

VSS is the engine that takes a point-in-time snapshot of your drive for backup. When something corrupts the VSS metadata — like a sudden power loss, a driver crash, or a pending reboot from an update — the snapshot fails the consistency check. The backup software then stops because it can't trust the snapshot. Simple fix: clean up VSS and let it rebuild.

The Fix: Step by Step

These steps work for Windows 10 and 11. You'll need an admin account.

1. Check free disk space
   Press Win + E to open File Explorer. Right-click your C: drive and select Properties. If free space is below 10GB, VSS can't make a snapshot. Free up space by deleting temp files: open Disk Cleanup (search for it in Start), pick the C: drive, check "Temporary files" and "Recycle Bin", click OK. After it finishes, free space should go up.
2. Run a disk check
   Open Command Prompt as admin: press Win + X and pick "Terminal (Admin)". Type chkdsk C: /f /r and press Enter. Say yes when it asks to schedule the check on next reboot. Restart your PC. This takes a while — could be an hour on a big drive. It fixes file system corruption that breaks VSS.
3. Reboot cleanly
   After chkdsk finishes, do a normal restart. Don't skip this — some VSS writers only reset on a fresh boot.
4. List VSS writers
   After reboot, open Command Prompt as admin again. Type vssadmin list writers and press Enter. You'll see a table of writers. Look for any that say "Error" or "Not responding". If they all say "Stable" and "No error", you're good. If any show error, note the writer name.
5. Reset stuck VSS writers
   For a specific writer like "System Writer" that's stuck, run this in the admin Command Prompt:
   

   net stop vss
     net start vss

   Then re-run vssadmin list writers to check if it's stable now. If it still shows error, you might need to restart the Volume Shadow Copy service: net stop vss /y (force stop) then net start vss.
6. Delete old snapshots
   Old snapshots can cause conflicts. In the admin Command Prompt, type vssadmin delete shadows /all /quiet. This removes all previous snapshots. Don't worry — it only deletes the shadow copies, not your files. After this, VSS will make a fresh snapshot next backup.
7. Register VSS DLLs
   This re-registers the VSS components. In the admin Command Prompt, run these one by one:
   

   cd /d %windir%\system32
     regsvr32 /s ole32.dll
     regsvr32 /s oleaut32.dll
     regsvr32 /s vss_ps.dll

   Each will say "DllRegisterServer succeeded". Ignore any error about vss_ps.dll — that's normal for some systems.
8. Restart the backup software
   Now try your backup again. For Windows Backup, go to Settings > Update & Security > Backup and run it manually. For third-party tools, open them and start a new backup job.

If It Still Fails

If the error comes back, check these three things:

• Check for pending restarts — Open Settings > Windows Update and see if it says "Restart required". A pending update often blocks VSS. Do that restart first.
• Look at your antivirus — Some antivirus tools (especially Norton and McAfee) lock VSS writers. Try disabling real-time protection temporarily. If the backup works, add an exception for the backup tool.
• Check disk health — Download CrystalDiskInfo (free) and check your C: drive health. If it shows "Caution" or "Bad", the drive might be failing. That causes VSS to give up. Time to replace the drive.

The real fix is almost always freeing up disk space and deleting old snapshots. I've seen this work on hundreds of machines. Give it a shot.