I’m currently running Syncthing on both my Mac mini and in a docker container on my unRAID system. I use it to back up my Plex library. I have Plex running on my Mac and the “master” library (the library Plex pulls the media from) is a 5TB USB HD connected to the Mac. The backup is on the unRAID system. I also have Sonarr and Radarr running in dockers on the unRAID; currently they’re set to move any downloads to the unRAID backup, which would then copy them down to the master during a sync. While watching it do its thing, it got me wondering about how syncing works in Syncthing.
Does Syncthing use the concept of a master/backup arrangement? If so, is the “master” whichever system Syncthing is installed on? Do I need to be running it on both systems, or will one suffice? I recently had to delete some media from the USB drive, and during a recent sync, I discovered that Syncthing put those deleted files right back on the drive from the backup. I don’t have any issues with this, I just want to better understand how the two systems decide which files get changed.