Windows 11 Robocopy Wizards

[oldgreyguy]

Have an issue with Robocopy, thought you boys & girls might give your opinion/observations on how to resolve this.

1/ Windows 11 computer running EM Client (c:\

2/ RoboCopy Command -- robocopy "C:\users\curtis\documents\em client" "E:\Email" /E /DCOPYAT /R:3 /W:5 /V

3/ Em Client folder = 51.1 gb

4/ first time running, took about an hour (1TB flash deive , formatted NTFS)

5/ second run, 30 mins later, took somewhere about 7 hours...Arrgh

assumptions... the above command should have skipped duplicate files (EM Client was not opened between the two runs

Help me mr. wizard(s)

 

[ChatGPT]

Hi oldgreyguy — your assumption is basically correct: Robocopy should skip files that are identical by name, size, and timestamp. A second run taking 7 hours usually means one of these is happening:

Most likely causes​

1. It is not recopying everything, but it is slowly scanning/comparing everything
   • Robocopy still has to walk the whole source and destination tree.
   • If the eM Client folder contains many small files, a USB flash drive can be painfully slow at metadata reads.
2. The flash drive is the bottleneck
   • Many 1 TB USB flash drives have terrible sustained write/read performance.
   • Some also slow down badly after the first large write because their cache fills.
3. Timestamps are not matching exactly
   • Even on NTFS, removable drives/controllers sometimes cause timestamp precision weirdness.
   • Add /FFT to allow a 2-second timestamp tolerance.
4. /V is making the run much slower
   • /V creates verbose output for skipped files too.
   • Console output is surprisingly expensive when there are many files.
5. Something is touching the eM Client files
   • eM Client may not be open, but Windows Search, antivirus, backup software, or sync tools may still touch files.
   • If timestamps or attributes change, Robocopy may think files are different.

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First thing I would try​

Run this version instead:
robocopy "C:\Users\curtis\Documents\em client" "E:\Email" /E /COPY:DAT /DCOPY:DAT /R:3 /W:5 /FFT /XJ /MT:8 /NP /NFL /NDL /LOG:"%USERPROFILE%\Desktop\emclient-robocopy.log"

What changed​

• /COPY:DAT explicitly copies data, attributes, timestamps.
• /FFT relaxes timestamp comparison.
• /XJ avoids junction-point weirdness.
• /MT:8 uses 8 threads.
• /NP removes percentage progress output.
• /NFL /NDL suppresses file/folder listing.
• /LOG: saves the useful summary without flooding the console.

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To find out whether it is really recopying files​

Do a test-only dry run:
robocopy "C:\Users\curtis\Documents\em client" "E:\Email" /E /COPY:DAT /DCOPY:DAT /R:3 /W:5 /FFT /XJ /L /V /TS /FP /LOG:"%USERPROFILE%\Desktop\emclient-dryrun.log"

Important​

/L means list only. It will not copy, delete, or change anything.
After it finishes, check the summary at the bottom of the log. Look especially at:

Files :        Total    Copied   Skipped  Mismatch    FAILED    Extras
Bytes :        Total    Copied   Skipped  Mismatch    FAILED    Extras

If Copied is near zero, Robocopy is skipping correctly and the delay is mostly scanning/logging/USB speed.
If Copied is large, then timestamps/attributes/content are changing.

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If you want the destination to be an exact backup mirror​

You can use /MIR, but be careful:
Warning: /MIR deletes files from E:\Email that no longer exist in the source.
Test first:
robocopy "C:\Users\curtis\Documents\em client" "E:\Email" /MIR /COPY:DAT /DCOPY:DAT /R:3 /W:5 /FFT /XJ /MT:8 /NP /L
If the preview looks safe, remove /L:
robocopy "C:\Users\curtis\Documents\em client" "E:\Email" /MIR /COPY:DAT /DCOPY:DAT /R:3 /W:5 /FFT /XJ /MT:8 /NP /NFL /NDL /LOG:"%USERPROFILE%\Desktop\emclient-mirror.log"

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My practical recommendation​

For this job, I would use:
robocopy "C:\Users\curtis\Documents\em client" "E:\Email" /E /COPY:DAT /DCOPY:DAT /R:3 /W:5 /FFT /XJ /MT:8 /NP /NFL /NDL /LOG+:"%USERPROFILE%\Desktop\emclient-backup.log"
If the second run still takes hours, I would strongly suspect the USB flash drive, especially if the log shows most files were skipped.
A proper external SSD will likely make this job dramatically faster than a 1 TB thumb drive.

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One question​

Can you post the Robocopy summary section from the bottom of the second run? That will tell us immediately whether it spent 7 hours copying or just scanning/comparing.