I am better trying to understand how syncthing works between devices.
If I share a folder type with send/receive to multiple devices (Original device) shared to 2 separate other devices. Lets say everything is synced.
If the original device is shut off, and other device #1 makes a change, will the change be propagated to other device #2? Or does it need the original device to be active to sync the changes?
Welcome here @zerosl !
There is no “original” device. All are equal.
Changes will propagate between all connected devices, regardless of which devices are connected.
It’s described in detail at Understanding Synchronization — Syncthing documentation —- essentially, when a device reconnects after being down or out of communication, all the devices agree on a “global” version of each file. Each device works to get whatever updates are needed for the local version to match the global version.
The two other devices will only sync with each other if you connected them directly as well and shared the folder mutually. Otherwise sync will happen when the other device #1 has connected to the original device again, and after that other device #2 connects to the original device.
It’s up to you what connections you make. In this simple case, you get either a linear topology A - B and B - C. Or if you add the direct connection A - C, you close a triangle, figuratively. Either way will work, just with different characteristics.