0XC000A2A4

Fix STATUS_OFFLOAD_WRITE_FILE_NOT_SUPPORTED (0XC000A2A4)

EP
Erropedia Team
📅 August 28, 2026 📅 Updated Sep 12, 2026 👁 18 views Cybersecurity & Malware Intermediate
This error usually pops up when copying large files to a NAS or external drive. Here's how to fix it fast, without touching your hardware.

Yeah, that error's a pain – you're just trying to move a folder of photos or a VM backup, and Windows throws 0XC000A2A4 right in your face. Let's get you back to copying stuff.

The Quick Fix: Disable Copy Offload in the Registry

The fastest way to kill this error is to turn off the offload write feature that Windows uses for network transfers. Open an admin command prompt and run this:

reg add "HKLM\SYSTEM\CurrentControlSet\Control\FileSystem" /v DisableCopyOffload /t REG_DWORD /d 1 /f

Then reboot. That's it. If you're on Windows Server 2016 or 2019, you can also use the PowerShell command:

Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem" -Name DisableCopyOffload -Value 1 -Type DWord

After the reboot, try copying the file again. For most people, that's the end of it.

Why This Works

Here's what's actually going on. Since Windows 8 and Server 2012, Microsoft built in a thing called "copy offload." It's supposed to make copies faster by telling the storage device to move data directly, without bouncing it through the system's memory. It's great when you're copying between two NTFS drives on the same machine.

But when you're copying to a network share – especially a NAS from Synology or QNAP – the server might not handle that offload request. The Windows client asks, the server says "Nope," and instead of falling back to a normal copy, Windows just throws that 0XC000A2A4 error. It's a dumb situation, because any decent OS would just do a standard copy instead of failing. But here we are.

Disabling copy offload forces Windows to always use the plain old copy method, which every server understands. You lose a little speed, but honestly, most of the time you won't notice unless you're copying terabytes.

Variations of This Issue

Sometimes the registry tweak doesn't cover all the bases. Here are a few other things I've seen cause the same error code:

1. The Destination Is FAT32 or exFAT

If your external drive is formatted as exFAT or FAT32, Windows sometimes tries to offload writes there too, and the drive's filesystem driver doesn't support it. The fix is the same registry change, or you can just reformat the drive to NTFS if you don't need Mac compatibility.

2. SMB Version Mismatch

Older NAS boxes running SMB 1.0 (which you should never use anymore) or SMB 2.0 can choke on offload requests. I had a client last month with an ancient Buffalo NAS that would give this error on any file over 1GB. We updated the NAS firmware and enabled SMB 3.0, and it cleared up without the registry hack.

To check your current SMB version, run this in PowerShell:

Get-SmbConnection | Select ServerName, Dialect

If it shows something like "2.0.2", that's your clue.

3. Third-Party Storage Drivers

Some backup software (looking at you, older versions of Acronis and Veeam) install their own filter drivers that can interfere with offload operations. If the registry fix doesn't work, check if you have any storage-related filter drivers:

fltmc

Look for anything that isn't part of a standard Windows install. If you see something from a backup tool, try disabling it temporarily or updating it.

4. Cluster Shared Volumes on Hyper-V

If you're running Hyper-V and the error appears when managing VMs on a CSV, you might also need to disable CSV offload separately:

Set-ClusterStorageSpacesDirect -EnableOffload false

Or if you're on a regular cluster:

Set-VMHost -EnableServerMessageBlock1 $false

That one's rare, but it happens.

Prevention

The registry fix is persistent, so you won't see this error again on that machine. But there are a couple of things you can do to avoid the whole mess in the future:

  • Keep your NAS firmware and Windows updates current. Most modern NAS boxes support SMB 3.1.1, which handles offload gracefully.
  • If you're setting up a new server, make sure to enable the "SMB 3.0" feature and not just the older SMB 1.0 role.
  • For any external drive you buy, reformat it to NTFS if you're only using it with Windows. It'll save you from a bunch of weird errors, not just this one.

The registry tweak is a one-time thing, and it's not going to break anything else. I've applied it on dozens of machines, and the only side effect I've seen is that copies to network shares are maybe 10% slower – worth it to get your work done.

Go run that command, reboot, and get back to copying. You've got better things to do than fight with a registry key.

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EP
Erropedia Team
Tech Support Editors
The Erropedia editorial team researches and documents real-world tech errors from across Windows, Linux, macOS, networking, databases, cloud platforms, and more. Every solution is reviewed for accuracy and updated as software and systems evolve.