It's frustrating to be trying new things and they don't work, but there is nothing so irratating as something failing that you thought worked and consequently rely upon. These last few weeks I've been struggling with a file sharing bug in Trend Micro's anti-virus program, though as with all these antivirus software originated problems, they don't tell you that. Here's the bug report I was writing up while investigating and crucially the simple solution.

I'm trying to copy a virtual machine (VM) instance from one machine to another over a 1GB LAN.

I have no problem connecting between the machines. There's plenty of free space on both. I can copy small groups of files quite reliably, but copying large groups of large files (such as a VM) consistently causes the Windows file sharing client to report this problem mid way through:

There is a problem accessing \\\
Make sure you are connected to the network and try again.

Here's my setup:

* Client: Windows 7 Professional PC, no domain
* Server: Mac Mini, OSX, HFS+ external drive hosting samba share

Transfer fails after copying a different amount of data each time, but all about 5GB:

Trial 1: 4.96GB
Trial 2: 5.36GB
Trial 3: 5.36GB

Transfer fails on different file every time:

Trial 1: testbed-s005.vmdk
Trial 2: testbed-s006.vmdk
Trial 3: testbed-s006.vmdk

After a trial fails, I can successfully copy the file on which it failed in isolation, so it doesn't seem to be a space issue.

A Wireshark analysis showed that the 'stop' command was originating from, which is the client machine, but why?

I looked at these solutions to other problems in the hope of solving mine:


Evaluation: does not apply because transfer is across a LAN and the failure is not after a consistent volume of data has been transferred.

I tried these things to find a working solution:

Solution: turn off Trend Micro Titanium Internet Security (anti-virus program on client)

Result: transfer completed successfully. I tried it a second time and again it worked perfectly.


Realising at this point that it was almost certainly another anti-virus problem wasting my time I re-enabled my antivirus program (Trend Micro) to discover that the transfer got interrupted again! I redisabled it and did one final test.

I can say confidently that Trend Micro Titanium Internet Security is interrupting my large file set transfers.

Ultimately the solution was simple. I added a folder exception to its 'scanning and monitoring', and transferred worked properly again. If only Trend Micro had shown me pop-up to say "we've interrupted a large file transfer to your computer, click here to override", I wouldn't have had to spend half a day debugging it.

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