How to fix Error 420 on Windows 11

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Troubleshooting Guide: Error 420 – “This Operation Requires a DAX Volume”

Why This Error Happens

This error occurs when an application or API call attempts to perform a Direct Access (DAX) operation—such as memory-mapped file access—on a volume that does not support Direct Access storage. DAX requires the underlying storage to be backed by persistent memory (PMem) hardware or a properly configured Storage Spaces Direct (S2D) volume formatted specifically for DAX mode. If the target drive is a standard NTFS volume on conventional SSD/HDD storage, or if the persistent memory module isn’t correctly initialized in the BIOS/UEFI, Windows 11 will reject the DAX-specific I/O request and return Error 420.

Step-by-Step Resolution Guide

  1. Verify Persistent Memory Hardware Presence
    Open Device Manager → expand System Devices → confirm an entry exists for “NVDIMM” or “Persistent Memory Controller.” If absent, DAX volumes cannot be created regardless of software configuration; check physical PMem installation and BIOS/UEFI settings (enable “PMem” or “NVDIMM Support”).

  2. Check Existing Volume Configuration
    Open PowerShell as Administrator and run:

   Get-PmemDisk
   Get-Volume | Select-Object DriveLetter, FileSystem, DedupMode

Confirm the target drive letter is associated with a Persistent Memory disk, not a standard SSD/HDD.

  1. Create or Reformat the Volume as DAX-Enabled
    If the volume exists but wasn’t formatted correctly, recreate it with DAX support explicitly enabled:
   Get-PmemDisk | New-PmemDisk 
   New-Volume -DiskNumber <PMemDiskNumber> -FriendlyName "DAXVolume" -FileSystem ReFS -IsDax $true -DriveLetter <TargetLetter>

Note: DAX mode requires ReFS or NTFS with DAX-compatible formatting; standard volume creation via File Explorer does not enable this flag.

  1. Update Persistent Memory Drivers
    Go to Settings → Windows Update → Advanced Options → Optional Updates → Driver Updates, and install any pending NVDIMM/PMem controller driver updates from your hardware vendor (Intel, Dell, HPE, etc.).

  2. Redirect the Application to the Correct Volume
    If DAX hardware/volumes aren’t available in your environment, reconfigure the requesting application (e.g., a database or virtualization tool) to point to a standard volume instead of requesting DAX-specific access, if the application supports a fallback mode.

Alternative or Verification Steps

  • Verify the fix: Run fsutil fsinfo volumeinfo <DriveLetter>: in an elevated Command Prompt and confirm the output includes DAX volume: YES.
  • Alternative: If no physical PMem hardware is available, use Storage Spaces Direct (S2D) with emulated persistent memory in a lab/test environment, or disable the DAX-specific feature in the application’s configuration file to bypass the requirement entirely.