5 ms·

I just experienced an interesting exFAT issue yesterday. Apparently it has a 2 second resolution on mtime. Got a bug report and just formatted a new partition w

I just experienced an interesting exFAT issue yesterday. Apparently it has a 2 second resolution on mtime. Got a bug report and just formatted a new partition with exFAT in windows 11 and it was unable to set modified timestamp to an odd number. Or rather i got no error when setting it, but it did get rounded up if it was odd. The wiki entry for exfat says it has 10ms resolution up from 2s in FAT, but that didn't seem to be the case for me. I thought about it being FAT and windows just lying to me but i couldn't confirm that was the case.

fredoralive 4y ago
Looking at the specification[1], it seems ExFAT uses an old style 2 second granularity FAT timestamp, but with an extra separate single byte field to give 0-199 * 10ms extra for fine(r) grained time stamps. It's possible Windows just ignores the high resolution field? Bit odd for Microsoft's own implementation to ignore their own enhancements though. I do have to ask the idiot question that you are sure you formatted the drive as ExFAT and not FAT32? [1] https://learn.microsoft.com/en-us/windows/win32/fileio/exfat-specification#746-lastmodifiedtimestamp-lastmodified10msincrement-and-lastmodifiedutcoffset-fields https://learn.microsoft.com/en-us/windows/win32/fileio/exfat...
- farrisbris 4y ago
  I'm quite sure yes. https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getvolumeinformationw https://learn.microsoft.com/en-us/windows/win32/api/fileapi/... returns exFAT and it says exfat for that partition in the disk management tool.