I am synchronising folders between one Linux, two Windows 11, one Android 11 and one Android 12 device using Syncthing v1.23.1. One of these folders (Folder2 in log) is 4.36GB in size across 11853 files and 3445 folders. So it is fairly large but it does synchronise across all devices apart from the Android 11 device (Onyx Boox Note Air2 Plus). When I try to synchronise, it takes around 6 hours to synchronise the 3445 folders and then stops at 0 files and stays there for half an hour before reporting this in the logs:
Then, every half an hour I get the same error message. My complete log is attached where you can see folder “Folder2” failing to synchronise on a device called “Android11Device”. I am happy to add any additional logging info or configuration details.
Notes:
This folder syncs across all other devices
I have another folder (Folder1 in log) on the same device which is 3.1GB over 279 files and 279 folders - it is syncing just fine
Since the folders seem to take so long to sync, I tried flattening my folder structure so that it was 4.36GB in size across 11853 files and only 32 folders - it didn’t help
I understand that there are issues with Android not being able to connect to a peer directly, so on my android device I specified the IP address of the peer specifically to try and avoid it connecting via a relay - it does seem to understand the LAN IP address of the peer but still connects to a relay
I have recreated the sync folder definition using all the default settings on the “Advanced” tab
I have read about some issues regarding Android 11 but if this was the cause then I would expect neither Folder1 not Folder2 to sync
As you’ve already observed, there are problems with local discovery on Android (i.e. it’s broken unless you run Syncthing as root). Because of this, you either need to keep global discovery enabled or hard-code IP addresses or hostnames. If the devices still can’t connect directly, it’s likely a problem with the network configuration, firewall settings, etc.
The very slow sync is unfortunately also expected on Android, especially with a large number of files. There isn’t anything that can really be done about it as it’s caused by the Android’s implementation of its filesystem access. The more files you’ve got in a folder, the slower the sync is going to be.
As for the stalled sync, can you add screenshots showing the Web GUI on both devices (with any possible error messages visible)? On Android, you can access it through the left slide-out menu.
Thank you very much for your reply - I appreciate the help.
If the devices still can’t connect directly, it’s likely a problem with the network configuration, firewall settings
Since I have another folder (Folder2) which is syncing between the same two devices without issue it feels like this is unlikely - but I don’t pretend to understand the inner workings of Syncthing. What could it be about the different folders that might be affected by the network config or firewall?
The very slow sync is unfortunately also expected on Android
I am happy with a slow initial sync - once I have got the initial sync finished the number of changes are not very frequent and only a few hundred kilobytes each time.
can you add screenshots showing the Web GUI on both devices (with any possible error messages visible)?
Sure, see below. There are no errors displayed other than those in the logs. I had anonymised the logs so I had to anonymise the screenshots of the WebUI too, but all names and IDs should match:
