Constant small file size changes on JPEG

[rjmusto]

Hi Guys,
Newbie here.

Running OSX 10.13.

I have a folder with (mostly) JPEG images, stored in 3 places:
an external drive, on iCloud and on a QNAP NAS.

The external drive is the master and I use FreeFileSync to sync up the other two.

I have found that running a sync Compare on these folders (that were previously synced) throws up the result that a lot of images stored on the NAS now have slightly different file sizes. So it looks like something is making changes to these files. The external drive to iCloud folders remain synced.

Ok, I should probably post this on a QNAP forum, but I have not found that a helpful or friendly place, so thought I'd see if anybody here has seen this problem.

Thanks,
Ralph

[Plerry]

Differences in occupied disk-space can be the result of different file-systems or block-sizes.
However, those should not affect the actual file-size.

Changes in file size and/or dates are often the result of Antivirus tools running on a system;
accessing, scanning and possibly modifying files.
Might that be the case for the QNAP?

[rjmusto]

Hi Perry,
Thanks for the reply.

I don't have antivirus running on the QNAP, so shouldn't be that.

It uses a Linux file system, so is it possible there is some conversion going on in saving the files that could cause this change?

[Zenju]

First thought: make a comparison with a hex editor.