Windows – VHD network file transfer fails consistently at 4GB

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This issue has been extremely frustrating for us: when transferring a large VHD (virtual hard disk) file from a Windows 7 machine over the network to a physical Windows Server 2008 machine at our datacenter, the windows file transfer fails at 4 GB consistently. We have a direct 100 mbit connection from our main office to our data center.

When the transfer fails, the error message we receive is:

There is a problem accessing \\server-name\d$
Make sure you are connected to the network and try again.

It is only VHD files larger than 4 GB that fail. If we send any other file type, it works fine. If we zip the VHD, that also works. Moreover, we can send a VHD the other direction (from the data center to the main office) no problem. It is just VHD files in that direction.

Important notes:

  • All partitions are NTFS!!
  • There is no firewall between workstation and server
  • We have tried disabling the antivirus on the workstation (no antivirus on server)
  • We have tried transferring the file from a machine not on the domain
  • We have tried transferring the file from a Ubuntu machine (still fails but at around 450MB instead of 4GB)
  • Wireshark capture shows 40 DUP ACKs when transfer fails
  • Xcopy and Robocopy (with restart flags) both fail (same point)
  • FTP transfer fails at 4,14X,XXX,XXX bytes and cannot be restarted at that point
  • We tried changing the file extension (stupid, but a last resort) to something other than vhd before sending it, but it still failed
  • Connection is as follows: Dell Workstation (Main Office) -> Dell PowerConnect 5448 Managed Switch (MO) -> HP Procurve 2910al-24G Layer 3 Router (MO) -> 100Mb TLS link -> HP Procurve 2910al-24G Layer 3 Router (Data center) -> Dell PowerConnect 5448 Managed Switch (DC) -> Dell Server (DC)

So basically, it is JUST vhd files > 4GB, from our main office to our datacenter that fails. This all just doesn't add up… at this point I believe it is a issue with our network hardware settings, but I don't understand what the difference is between transferring a large VHD (which fails, at 4GB) and a large video file (which works always).

Best Answer

After troubleshooting this for many hours (and trying all the suggestions posted here), the issue turned out to be the TLS link between our main office and the datacenter. I called our TLS provider and after talking to several NOC technicians, one of them had heard of the exact issue before. It turned out that some of their layer 2 equipment was old and had issues with VHD data.

The solution was upgrading the firmware on these devices, which was performed by the TLS provider. We now have no issues transferring large VHDs. For those interested, our TLS provider is Shaw Communications in Victoria, Canada.

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