NTFS compare to ExFAT

Open discussion about WinMerge.

NTFS compare to ExFAT

Postby ThomT » Fri Jul 24, 2020 2:18 pm

I used robocopy on my Windows 10 Pro system to copy a bunch of folders with .mp3 files to a flash drive. Robocopy allows me to preserve all of the files' original dates/times.

My hard drive is NTFS, and the flash drive is ExFAT.

Using Winmerge 2.16.6.0, 64 bit, to compare the results, it reports that every file and folder is "different", even though the dates, times, and file sizes are actually identical.

I assume this is because I have different file systems on the two drives.

Can anyone confirm this, and is there anything I can do about it?

(I have no choice about needed to use ExFAT for the flash drive -- the media player that it's being used in doesn't support NTFS yet.

Thanks.
ThomT
 
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Re: NTFS compare to ExFAT

Postby ThomT » Mon Jul 27, 2020 4:01 pm

My error -- there was a 1-second time difference between the original and the copy. I have no idea why Robocopy did that -- I need to do more research to figure that part out, but it's not WinMerge's fault.
ThomT
 
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Re: NTFS compare to ExFAT

Postby ThomT » Mon Jul 27, 2020 8:11 pm

More info: I've found the source of the problem. It's a limitation of FAT (and apparently also of ExFAT).

According to https://docs.microsoft.com/en-us/window ... dfrom=MSDN
"Not all file systems can record creation and last access times, and not all file systems record them in the same manner. For example, the resolution of create time on FAT is 10 milliseconds, while write time has a resolution of 2 seconds and access time has a resolution of 1 day, so it is really the access date. The NTFS file system delays updates to the last access time for a file by up to 1 hour after the last access."

So, it's not Robocopy, it's a fundamental constraint of FAT's write-time resolution, which can set the time off by as much as 2 seconds from the original.
ThomT
 
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