Starting with version 6.1.2, P5 outputs statistic file info in Backup Job logs.
This info gives an insight why files are saved, or saved again in incremental backups.
File lookup summary
This show the then number of files and folders that were found during the file scan in the filesystem(s).
The number of files that were missing in the index. In an Incremental backup these are new files.
The number of files that where renamed or moved to a different place but where already saved before
The number of files that where changed. This reflects an mtime stamp change, i.e. the file data was updated
x changed inode
The number of files that have changed attributed. This reflects an ctime stamp change, usually the ctime stamp is updated when a file owner, group or permission is updated. On Windows hosts, this reflects an updated archive bit. P5 translates that to a ctime change.
x changed size
The number of files where only the file size changed. In normal file systems this number will be zero as the mtime will change, too, so the file is listed as modified. The size change may be detected when files are saved via different protocols, for instance once via SMB and once via NFS.
x other type
The number of files that were replaced by folders or symbolic links (or other way round).
The number of files that must be saved again because the media that hold the last copy expires or is expired. This will only be set in backup jobs that run in progressive mode.
A further possibility for checking which files will be saved is the "Dry Run" Backup Job, this job type behaves like a normal backup, excepts that no files are saved to the target media and the Index is not updated.