When something does not happen as expected

The first place to look is always the log. At level Info it records what was copied and deleted; at Debug also which file was skipped for what reason.

A file is not copied

Files are copied again on every run although they are unchanged

The target stores the modification time more coarsely than the source, an NTFS or FAT disk as the target of a Linux disk, for example. The copy is then fractions of a second ahead of its original, and when comparing by Time the source counts as newer. The Tolerance in seconds on the Options tab catches this; it is at 0 if someone switched it off. A jump of exactly one hour on all files points to FAT after a change of summer or winter time, see there.

Nothing is deleted in the target although the option is set

Nothing is synchronised at all

An SSH connection fails

In all these cases the synchronisation concerned is skipped for this run: nothing is copied or deleted. The other synchronisations go on as usual.

A warning about a missing drive appears – or stays away

Whether an unreachable source or target is reported is decided per synchronisation by the option Warn if the drive or SSH connection is missing: switched on, there is a warning after Synchronise once and a warning line in the log, switched off only an info line. So if one synchronisation warns and another does not although both miss the same disk, the option is set differently on them. Everything else is under Unreachable drives and connections.

Bringing back deleted files

If the delete mode is set to Move to recycle bin, the files are in the recycle bin directory set there, in the structure of the place they came from. With Delete permanently and with targets over SSH there is no such copy.

If a target file was overwritten, the Generation principle helps – provided it was switched on beforehand: the previous version is then next to the file as .bak.1.