Fix STATUS_LOST_WRITEBEHIND_DATA_NETWORK_SERVER_ERROR 0XC000A081

30-Second Fix: Turn Off Write Caching on the Server

The culprit here is almost always write caching on the remote server's disk or controller. When a network client sends data, the server's disk caches it and reports success before actually writing it to disk. If the server crashes or loses power before that write happens, you get 0xC000A081 on the next client write.

1. On the server (not the client), open Device Manager.
2. Expand Disk drives. Find the drive hosting the network share.
3. Right-click that drive → Properties → Policies tab.
4. Uncheck Enable write caching on the device.
5. Also uncheck Turn off Windows write-cache buffer flushing if it's checked.
6. Click OK and reboot the server.

Test your file copy again. If the error's gone, you're done. I've seen this fix work on Server 2016, 2019, and 2022. It's the first thing I check.

5-Minute Fix: Disable SMB Leasing or Enable Strict Locking

If the caching fix alone didn't do it, the issue might be SMB 3.0's lease mechanism. Leasing lets clients cache writes aggressively, but on flaky networks it backfires. Disable it on the server side.

1. On the server, open PowerShell as Admin.
2. Run:
   

   Set-SmbServerConfiguration -EnableLeasing $false -Force

   This turns off SMB leasing for all shares. It forces the server to use older oplock behavior which is slower but rock solid.
3. If you want to keep it per-share instead, run:
   

   Set-SmbShare -Name "YourShareName" -ShareState DisabledLeasing

4. Also enable strict locking on the share:
   

   Set-SmbShare -Name "YourShareName" -ShareState EnabledStrictLocking

5. Restart the Server service: Restart-Service LanmanServer

Now test. This solved it for a client using VMware VMs with SQL Server databases on a NAS. The error stopped immediately.

15-Minute Fix: Update Network Drivers and Check Switch Settings

If you're still seeing the error, it's likely a network hardware or driver problem. Specifically, jumbo frames or flow control mismatches between the client and server can cause packet drops that trigger 0xC000A081.

1. Update the NIC drivers on both the client and server to the latest from the manufacturer (Intel, Realtek, Broadcom). Don't use Windows Update's generic drivers.
2. On both machines, open Network Connections → right-click your NIC → Properties → Configure → Advanced tab.
3. Disable Large Send Offload (LSO) and TCP Checksum Offloading. These often cause corruption over long transfers.
4. Set Jumbo Packet to Disabled if your switches don't support jumbo frames. Even if they do, disable them for testing.
5. Disable Flow Control on both ends.
6. Check your switch ports for errors. Log into the switch and run show interface counters errors (Cisco) or equivalent. If you see CRC errors, frame drops, or alignment errors, fix cabling or replace the switch port.
7. Reboot both machines.

This fix is overkill for most cases, but it's the right call when you've got hypervisors, SANs, or any network with high latency. The error often pops up during large file copies over 10 GbE links with mismatched MTUs.

When to Give Up and Call the Vendor

If none of these work, you're looking at a deeper problem:

• Check the server's event logs for disk errors (event ID 7, 11, or 153 from disk or ntfs).
• Run chkdsk /f on the server's volume — a corrupt MFT or bad sectors can mimic this error.
• Test with a different storage device (a USB drive attached to the server, for example). If the error goes away, the issue is the server's disk subsystem.

I've seen this error on HP ProLiant servers with broken RAID controllers and on Dell PowerEdge boxes with dying backplanes. Don't waste weeks on software fixes if hardware is the root cause.