Problem with folder stored on deduplicated volume.

I tried setup the Syncthing instance with folder backed on deduplicated volume, created by software.

After setup and beggining syncing I experienced a lot of errors with temp files similiar to:
INFO: Puller (folder "foldername" (foldernam), item "folder/filename.bak"): syncing: opening temp file: open /mnt/xxx/xxx/xxx/xxx/xxx/xxx/.syncthing.filename.bak.tmp: file exists
INFO: Folder "foldername" (foldername) isn't making sync progress - retrying in XmYs.

Indeed, as error message claims, the temp files actually exists.
Some files however have synced properly (about 70 from total 900).
Could you please shed some ligth, is the problem related with folder stored on deduplicated volume?

If the volume doesn’t behave like a normal disk surprising things can happen - for Syncthing and for other programs.

The FS behaves pretty normal, you can do any normal file operation. Could you explain what exactly the ‘file exists’ error means? Is this means the app doesn’t see the file in the folder then tries to create it as a new file? Can any folder / files permission issue be the reason?

The FS does not behave pretty normal, as it throws an error that a file exists, when being asked to open a file that exists. See below.

That’s probably us opening with O_CREATE | O_EXCL because we’re sure it doesn’t exist already and shouldn’t exist. But apparently it does. Which is odd. So yeah I don’t know, maybe the file system is just slow to react and shows files that have been deleted or doesn’t show files that were just created. In any case I think it boils down to “odd file system emulating thing doing it wrong”, unless you can reproduce on a normal file system.


You are right. It is odd FS behavior which you would not observe with manual CRUD file operations. I set the whole system up two times fron clean OS and for each time it didn’t work, with different error count of mentioned type. On the same machine (VM with Ubuntu 20.04), outside the deduplicated volume everything works fine, as expected. The whole instalation was done just for the prove of concept with high optimized storage in case of highly duplicated data (mix of Syncthing and Borg features :). This time it doesn’t work but I will try to achieve similiar feature maybe with other volume tools.
Thanx for your help.

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