Hi!
I've moved from robocopy as one user told me that FreeFileSync mantained a database to get change synchronization faster. As I see, when I run RealTimeSync, when it detects a change it runs a whole new cycle searching for all changes, instead of just syncing the change it detected. So when it comes to a huge folder where only a few files change, it takes a while to complete.
How can we get over this?
Avoid rescaning each cycle
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You could run a periodic sync instead. For realtime, you could break it up into smaller chunks. Unfortunately, I think it just reads the status of a Windows flag to detect changes, not that it finds the change itself, which means there is no getting around this.
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You are mixing up several things.
1) If you use FreeFileSync (FFS) to run a Two-way sync variant, it will always use a database (actually two databases, on on each side of the sync); when you run a Mirror or Update sync the use of the database is optional (checkmark "Detect moved files"). On the initial sync, the database does not yet exist and needs to be created. On any consecutive sync the database allows to detect moved (and renamed) files and folders, as long as they still reside in the left- or right-base-location or (sub)folders thereof (in a system that has stable file-IDs).
FFS is then able to rename/move the file or folder without renewed copying-over.
Still, FFS needs to read (scan) the entire left and right folder and file status and compare it to its local database file to determine which files have changed with respect to the status at the end of the previous sync, as stored in the database. This allows FFS to determine which files should be copied over (and, in case of Two-way, in which direction), which files to delete, and which to rename or (locally) move.
If you do not checkmark "Detect moved files" and run a Mirror or Update sync variant, FFS will also read (scan) the entire folder and file status of the left and right location. But instead of comparing to the left, respectively right local database, it will simply compare the left and right status to determine the sync actions (based on the selected sync method).
Using the FFS database is just another, more powerful method of comparing status and deciding on actions.
But in either case a full scan of the left and right folder and file status will be performed.
2) Upon detecting a change in a monitored folder, RealTimeSync (RTS) simply launches the specified application, normally an FFS sync. The FFS sync will then scan the full status of the left and right location, decides on sync actions execute those.
If you reads the listed limitations of RTS it should be clear why FFS always needs to do a full scan.
> How can we get over this?
With RTS and FFS you can't "get over this".
Are you aware of any other, cross-platform tools that can do this?
If not, it seems you have to "get over it". ;-)
1) If you use FreeFileSync (FFS) to run a Two-way sync variant, it will always use a database (actually two databases, on on each side of the sync); when you run a Mirror or Update sync the use of the database is optional (checkmark "Detect moved files"). On the initial sync, the database does not yet exist and needs to be created. On any consecutive sync the database allows to detect moved (and renamed) files and folders, as long as they still reside in the left- or right-base-location or (sub)folders thereof (in a system that has stable file-IDs).
FFS is then able to rename/move the file or folder without renewed copying-over.
Still, FFS needs to read (scan) the entire left and right folder and file status and compare it to its local database file to determine which files have changed with respect to the status at the end of the previous sync, as stored in the database. This allows FFS to determine which files should be copied over (and, in case of Two-way, in which direction), which files to delete, and which to rename or (locally) move.
If you do not checkmark "Detect moved files" and run a Mirror or Update sync variant, FFS will also read (scan) the entire folder and file status of the left and right location. But instead of comparing to the left, respectively right local database, it will simply compare the left and right status to determine the sync actions (based on the selected sync method).
Using the FFS database is just another, more powerful method of comparing status and deciding on actions.
But in either case a full scan of the left and right folder and file status will be performed.
2) Upon detecting a change in a monitored folder, RealTimeSync (RTS) simply launches the specified application, normally an FFS sync. The FFS sync will then scan the full status of the left and right location, decides on sync actions execute those.
If you reads the listed limitations of RTS it should be clear why FFS always needs to do a full scan.
> How can we get over this?
With RTS and FFS you can't "get over this".
Are you aware of any other, cross-platform tools that can do this?
If not, it seems you have to "get over it". ;-)
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- Joined: 26 Dec 2025
if i understand correctly, in ffs mirror mode and "use database file to detect changes", if rootfolder1\file1 is moved to rootfolder2, it can simply move it to folder2 and there's no need to delete the old file and re-copy into folder2?
if my right side is the backup hdd, i should use MIRROR mode but TWO WAY mode should still work since the right side/backup will always be older?
the database file is called "sync.ffs_db"? and is used by all the sync modes? if this time I used MIRROR mode and next time by accident I used the TWO WAY mode, it will still be compatible?
if I use FFS portable edition and downloaded a new version, I can just copy paste the database file into the new folder and it will work?
thank you
if my right side is the backup hdd, i should use MIRROR mode but TWO WAY mode should still work since the right side/backup will always be older?
the database file is called "sync.ffs_db"? and is used by all the sync modes? if this time I used MIRROR mode and next time by accident I used the TWO WAY mode, it will still be compatible?
if I use FFS portable edition and downloaded a new version, I can just copy paste the database file into the new folder and it will work?
thank you
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- Posts: 2978
- Joined: 22 Aug 2012
> if i understand correctly, in ffs mirror mode and "use database file to detect changes", if rootfolder1\file1 is moved to rootfolder2, it can simply move it to folder2 and there's no need to delete the old file and re-copy into folder2?
If rootfolder1 and rootfolder2 are both in the same left or right base-location (of your left-right sync pairs): yes (provided the OS and file-system of that base location has stable file-IDs between sessions).
> if my right side is the backup hdd, i should use MIRROR mode ...
Or the Update mode, if you want to retain files on your right side/backup that have meanwhile been removed from your left side/source.
> ... but TWO WAY mode should still work since the right side/backup will always be older?
Sounds correct
> the database file is called "sync.ffs_db"? and is used by all the sync modes? if this time I used MIRROR mode and next time by accident I used the TWO WAY mode, it will still be compatible?
Yes
> if I use FFS portable edition and downloaded a new version, I can just copy paste the database file into the new folder and it will work?
No.
Assuming "Use database file to detect changes" is checkmarked, after running the first sync, each left and right base location involved in a sync will contain a database file unique to that base location.
You should not move or copy any FFS database files.
If rootfolder1 and rootfolder2 are both in the same left or right base-location (of your left-right sync pairs): yes (provided the OS and file-system of that base location has stable file-IDs between sessions).
> if my right side is the backup hdd, i should use MIRROR mode ...
Or the Update mode, if you want to retain files on your right side/backup that have meanwhile been removed from your left side/source.
> ... but TWO WAY mode should still work since the right side/backup will always be older?
Sounds correct
> the database file is called "sync.ffs_db"? and is used by all the sync modes? if this time I used MIRROR mode and next time by accident I used the TWO WAY mode, it will still be compatible?
Yes
> if I use FFS portable edition and downloaded a new version, I can just copy paste the database file into the new folder and it will work?
No.
Assuming "Use database file to detect changes" is checkmarked, after running the first sync, each left and right base location involved in a sync will contain a database file unique to that base location.
You should not move or copy any FFS database files.
