[cybmole]

I am a regular user of freefilesync - in one -way ( mirror) mode. it backs up my calibre library & also my calibre app folder to a different hard drive

I have not noticed the issue under discussion. a typical backup finds only a few changed files which seems to equate to recent adds, deletes & edits. I dont think it is re-copying hundreds of opf files

PS I am using the last v5 of FFS, the UI for v6 looked very strange so I rolled back & disabled update notifications
update; tying harder to replicate this.

I ran my FSS mirror ( which writes to 2 separate backup locations ) there were ~100 changes

then I closed calibre & re-ran FFS compare , just a handful of changes detected: to metadata.db & related files
re-opened calibre, ran FFS compare again - same result

there are 2 compare settings in ffs, I use compare filze size & data. it could be that using compare content gives a different result?

I. Compare by File time and size
This variant considers two files with the same name as equal when both modification time and file size match. The following categories are distinguished:

file exists on one side only
left only
right only
file exists on both sides
different date
left newer
right newer
same date
equal
conflict (same date, different size)


II. Compare by File content
Two files with the same name are marked as equal if and only if they have the same content. This option is more useful for consistency checks rather than backup operations since it is naturally slower. The file modification time is not taken into account at all.