Wrong modification times?

[limmelimm]

I'm not sure, whether it's my fault or ZFSonLinux or OpenZFSonWindows or Windows itself. I couldn't find anything on the web about that.

It concerns my ZFS drive which is a backup drive of an NTFS drive (both external USB drives).
If I plug these drives into my Lubuntu 20.04 LTS machine (with "ZFS on Linux"), the modification times of the files on the NTFS-drive match with those on the ZFS-drive. All files.
But if I plug the drives into my Windows 10 or my Windows 7 machine (OpenZFSonWindows 0.24), the modification times of some files on the ZFS drive now are a few seconds younger than on the NTFS drive. I didn't touched them meanwhile. It's the same files. No modifications.

So on my Lubuntu:
xyz.txt = 12.02.2013 - 13:23:45 (NTFS drive)
xyz.txt = 12.02.2013 - 13:23:45 (ZFS drive)

On Windows:
xyz.txt = 12.02.2013 - 13:23:45 (NTFS drive)
xyz.txt = 12.02.2013 - 13:24:38 (ZFS drive)

As I wrote: just some files. And never older, always younger - but never more than . . . . mhhhh maybe 90 seconds. Some are 25 seconds younger, others 85. It's a detail, but it sabotages folder synchronization and surely other things.

I tried to discover any pattern in the affected files and the amount of seconds, but unfortunately it appears pretty random to me -.-*

The ZFS pool was created with "ZFS on Linux" of my Lubuntu and I also did all the data copying from the NTFS drive to the ZFS drive on my Lubuntu machine - never with OpenZFSonWindows. So maybe it has some difficulties with reading or interpreting the file properties of - let's say - "foreign" ZFS pools?

[lundman]

It is more likely it is the Windows version that is displaying the wrong time, sometimes. "time" is stored quite differently on Windows, and the areas where you have to return it (and look it up from disk) is also different. It could be more of a case that date returned actually belongs to some other item recently looked up (when listing, don't forget it sorts before displaying, so you don't know which one was returned by ZFS first).

It isn't something to be worried about (in terms of "changing what is on disk", but rather a display issue...

[limmelimm]

I think so, too. The modification times only differ on OpenZFSonWindows. All other machines are good.

It's an interesting idea to think of how ZFS delivers the files to the Windows Explorer. I didn't know that of course. But I don't have the impression, that it actually swaps the modification times of the some files. I really have the impression, that it always adds some seconds. Firstly: the times of the affected files are all very very close to the original ones. It's always just a few seconds.No hours, no days, no months, no years. Just less than 90 seconds. And secondly: it's always younger, never older. So I can eliminate swapping for sure.

But you're right. OpenZFSonWindows don't actually write these wrong modification times into the file's properties. It just displays them wrong.

I can't do any folder synchronization this way but that's okay with me since I can use Linux instead. I just didn't know whether it's a known thing or my fault and I wanted to let you know about these rebellious seconds.