How to fix Error 438 on Windows 11

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Troubleshooting Guide: Error 438 – I/O Request Could Not Be Coordinated with a File Snapshot Operation

Why This Error Happens

Error 438 occurs when the Volume Shadow Copy Service (VSS) is unable to synchronize a read/write I/O request with an in-progress snapshot operation, typically due to a timing conflict between the requesting application and the shadow copy provider. This is commonly caused by a corrupted or outdated VSS writer, insufficient disk space on the volume being snapshotted, or conflicting third-party backup/antivirus software intercepting the I/O request. In some cases, a stalled or crashed VSS-related service leaves the snapshot metadata in an inconsistent state, causing subsequent I/O requests to fail coordination checks.

Step-by-Step Resolution Guide

  1. Check VSS Service Status
    Press Win + R, type services.msc, and press Enter. Locate Volume Shadow Copy, right-click → Restart. Also restart Microsoft Software Shadow Copy Provider if present.

  2. Verify VSS Writers Are Stable
    Open Command Prompt as Administrator and run:

   vssadmin list writers

Look for any writer showing a state other than “Stable” or an error code. If found, restart the associated service (e.g., restart the SQL Server service if SqlServerWriter shows an error).

  1. Free Up Disk Space and Check Shadow Storage
    Run the following to inspect shadow copy storage allocation:
   vssadmin list shadowstorage

Ensure the volume has at least 10-15% free space. If storage is nearly full, resize it:

   vssadmin resize shadowstorage /for=C: /on=C: /maxsize=20GB

  1. Temporarily Disable Conflicting Software
    Disable third-party antivirus or backup applications (e.g., Acronis, Veeam) temporarily via Task Manager > Startup apps or their native UI, then retry the failing I/O operation to see if the conflict resolves.

  2. Re-register VSS DLLs
    In an elevated Command Prompt, run the following commands sequentially to re-register core VSS components:

   regsvr32 /s ole32.dll
   regsvr32 /s vss_ps.dll
   vssvc /register

Restart your PC afterward.

Alternative or Verification Steps

  • Verify the fix: Re-run vssadmin list writers and confirm all writers show a “Stable” state with no error codes, then retry the original backup/snapshot task that triggered Error 438.
  • Alternative fix: If the issue persists, run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth to repair underlying system file corruption that may be affecting the VSS framework.