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I've copied cca 180 GB using xcopy SRC DST /C /E /Q on Windows 10. The Files are mostly video files and/or presentations (ppt/pptx/pdf). I've noticed strange behavior: some of the copied files (2133 of 9268) has another checksum that original files. This means that the content of file have been changed during copy. I've checked several of those different files using WinMerge and seems that only tiny part of file were changed (see screenshot). I was first assumed that this part belongs to some metadata of file (owner, create date etc.) but then I realized that metadata are not stored in file itself. Why this happened? Can I somehow check if those files are the same (Seems like they are e.g. when I play video I see no difference)? Thanks

PS: I've used xcopy because first time when I've tried copy those files using totalcmd or explorer I get some errors and I've to press retry to skip or try again.

PPS: All files has the same size. I've also noticed hat several files in DST were only composed of ASCII 0 characters. I've recopied those files again using totacmd with no problems.

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  • It's probably because of "some errors" you were getting in Explorer/TotalCmd, but which were silenced with /C switch. Computers don't just throw errors randomly, errors indicate a problem.
    – gronostaj
    Commented Feb 8, 2017 at 20:31
  • @gronostaj yes this is true but when i pressed retry enough times in totalcmd file was copied. So i've assumed that /C will do this for me. I do not understand why there were errors cause both hdd are relatively new.
    – Wakan Tanka
    Commented Feb 8, 2017 at 20:43
  • Still, errors indicate some kind of a problem. Retrying until it works doesn't solve that problem. You can't tell what causes errors without actually knowing what they are, so we can't really help you unless you can provide more error messages.
    – gronostaj
    Commented Feb 8, 2017 at 21:04

2 Answers 2

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xcopy appears to have been deprecated by MS. Theoretically, it should have copied the files verbatim, but has obviously failed, as shown by your careful comparison. Most video formats are somewhat fault-tolerant, so are still viewable, but it does appear they have been damaged.

The issue might be the use of the /C, continue-on-error, option. With "healthy" media, there should be no errors. You might try using the /V option to verify files. If verification fails, then there is an issue such as bad media (e.g. a failing HDD or CD) or system noise. BTW, /J might be useful for large files, e.g. videos.

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You could try Microsoft's Robocopy (Robust File Copy), which is more of a folder copier rather than a file copier. Basic syntax from the CLI is "Robocopy source target", e.g. Robocopy C:\mysource E:\mytarget

There are also GUIs for Robocopy, read more from Wikipedia here

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