Can you skip the initial sync if all folders already have the same data?


Me and my friends are currently producing music / mixing together and we all have massive playlists that we would like to share for our sessions. That being said, instead of bringing our personal external drives each time, I decided that it would be easier to just setup Syncthing and share the whole thing. However, I have about 100GB+ of content, and not only it would be really long to transfer, but two of my friends have a pretty lame internet plan and they would bust their monthly limit real quick. So, I was thinking of transferring my actual content physically to their computer (using my external hard drive), and then sync my folder. However, will Syncthing overwrite all the files already there (and hence bust their internet), or it will be smart enough to detect that the files are identical (by checking the metadata or something)? If not, what should I do?

TL;DR : I want to be able to start with base data before syncing. In other words, when you usually sync a folder, you have to choose a destination path and it will automatically download all the content into this folder. In my case, I want this destination folder to already have the data and hence skip the initial sync.


Yes, you can do that. Syncthing first does a scan to index everything that is already on the disk, then it will compare to what other devices with the same folders have and sync if necessary.

Okay, but when doing this first scan, does Syncthing check the file content or the metadata? Because if Syncthing is checking file content, the data shared across the internet would be the same as downloading the files (in order to be able to compare the different versions).

The contents are checked, by hashing and comparing hashes. Not by sending the content to compare.

Oh okay, I see. How lightweight is this process (in terms of space)?

~48 bytes of metadata per 128 KiB of on disk data.

Interesting! Thanks a lot.

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