On 11/30/23 17:26, LateJunction wrote:

I created a ‘full’ backup against my most important folder tree – about 250 GiB, containing about 50K items. It took far longer than I expected, but did complete. I did not use checksum. I did specify that the folder tree was to be checked for changes every 12 minutes. I then made a single file change as a test – an important change to an important file. 4 hours later BIT had still not made an incremental backup, but rsync has been running, consuming about 1% of my reasonably fast CPU throughout that time. A simple running of FreeFileSync comparing the current folder tree with the full backup made 4 hours ago immediately shows the one file I changed, but BIT has not seen it – meaning that this change might be lost if I restore my ‘original’ folder tree now.

This loss of data is not what I expected. Why does it happen?

What file system type are you using on your host and backup medium files?

You can reply with the output of the "df -T" command, which will show this information for all mounted file systems.

Is your backup medium directly connected to your computer, or is it accessed via a network connection?

To make use of the "hard link" features BIT expects, you must be using a file system that supports this feature. All native Linux file systems do, but non-native file systems may not. This could result in BIT copying all 250 GiB every time.