I have two NTFS formatted drives on different machines and I do a robocopy mirror between them like this:

robocopy "D:\My Documents" "X:\Backup\My Documents" /MIR /V /NP /XD .* /XO /XA:SHTO /FAT /Z /ETA /DST /R:3 /W:30

But it will falsely mark files as newer, but I haven’t altered it, and it is a lots of files so I don’t think windows have altered them either.

I am running the robocoy in a steady loop and it takes about 15 minutes, so I think something is a bit wrong, anyone have this issue?

Example output:

  • same 17548 draft1.jpg
  • same 98108 draft2.jpg
  • same 104 Spiral3DCopy1.mtl
  • Newer 104 Sphere3DCopy1.mtl
  • Newer 345985 swamp1.jpg
  • Newer 75209 test.jpg

I have done a compare and no differences are found:

C:\>fc D:\Documents\"My Documents"\3d\Sphere3DCopy1.mtl X:\Backup\"My Documents"\3d\Sphere3DCopy1.mtl
FC: no differences encountered
  • Is the time set right on both machines? – Sven Jan 29 '12 at 16:46
  • Yes, it is, not all files is marked "newer" about 20% maybe – Cinaird Jan 29 '12 at 16:52
  • Is there anything common about the filetypes that are getting marked newer? – Trevor Sullivan Jan 30 '12 at 17:54
  • @TrevorSullivan: No, it is randomly distributed among my most common filetypes in the folder. Here is a sample of the most common filetypes: mtl, obj, jpg, png, pdf, pdf, odt, html, txt, psd, rar – Cinaird Jan 30 '12 at 20:41
  • 1
    And one more idea. Try running it with /L. This will do a "what if" scenario, without actually making changes. Let robocopy tell you which files it thinks are newer. Then pick one or two and go check the timestamps on both machines and see if they are actually different. Honestly, you've got a very odd situation, and it makes me think you've got some rogue program changing timestamps on you. – Larry Silverman Feb 5 '12 at 16:04

We found that using the /FFT Robocopy switch will reduce the timestamp to about 2 seconds difference when comparing file changes. It eliminated the 2 hours copying everything when the changed files would normaly take under 3 minutes.

RoboCopy /? says to use this switch to "assume FAT File Times (2-second granularity)."

Thanks to the folks at connetrix.


Try this:

robocopy "D:\My Documents" "X:\Backup\My Documents" /FFT /MIR /V /NP /XD .* /XO /XA:SHTO /FAT /Z /ETA /DST /R:3 /W:30

It worked for us.

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