Robocopy appears to do nothing when /MT flag is used

Question

This command works:

robocopy \\build7\d$ d: *.*  /mir  /XD "System Volume Information"  /XD "$Recycle.Bin"

But when I try adding the /MT flag:

robocopy \\build7\d$ d: *.*  /mir  /XD "System Volume Information"  /XD "$Recycle.Bin"  /MT

The only output I get is

-------------------------------------------------------------------------------
   ROBOCOPY     ::     Robust File Copy for Windows
-------------------------------------------------------------------------------

  Started : Thu Apr 09 09:11:27 2015

   Source : \\build7\d$\
     Dest : D:\

    Files : *.*

 Exc Dirs : System Volume Information
            $Recycle.Bin

  Options : *.* /S /E /COPY:DAT /PURGE /MIR /MT:8 /R:1000000 /W:30

------------------------------------------------------------------------------

It gives me that output, and then just sits there.

I tried using the /LOG flag to redirect the output to a file, but it still just sat there with the same output, only in a file.

Is it doing something in the background that I can't see, or am I doing something wrong?

Have you verified that your version of robocopy supports mulitthreading? — Zahra, May 28 '15 at 20:35
I have a similar problem, but the command does show output and finish (rather fast) with the /mt option. It is just that it does not copy any files. Seems to happen especially when combined with /xf and /xd. It is also worth noting that I copy files from a virtual share created by Microsoft Remote Desktop for Mac. Without /mt, files are copied as expected, but the command is slow even when there are no changes to copy. — Otto G, Jul 28 '23 at 17:51

score 12 · Answer 1 · answered Apr 15 '15 at 18:08

In my experience, what you are seeing is normal. When Robocopy runs using multiple threads (/MT), the output is limited to exceptions (new file, extra dir, error, etc...). It will not show you the directory names with the file count that you are probably used to seeing. That means that if the target is largely in-sync with the source, you will not see much output.

I don't know exactly why this is the case. I assume that Robocopy handles the directory walking differently when there are multiple threads involved. This difference probably makes the normal output impossible (or meaningless) to produce.

When I am running Robocopy with multiple threads, I often use the Disk tab in the Windows Resource Monitor to see what Robocopy is doing. How to Use Resource Monitor

When on the Disk tab, you can check "Robocopy.exe" in the "Processes with Disk Activity" section to ensure you're only seeing transfers from Robocopy. Even though I used `/MT:4`, the number of touched files started being larger than 4 over time. It appears to be starting new transfers as other files near completion. — Kevin Ghadyani, Dec 12 '19 at 05:12

Robocopy appears to do nothing when /MT flag is used

1 Answers1