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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
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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
Are these machines in different time zones? I'm wondering why you're using /DST and whether it could somehow be to blame. – Larry Silverman Feb 1 '12 at 15:16

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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