Sync becomes very slow between Mac and Android device

[macsync (Mac)]

Hi, I’m using Syncthing 1.27.2-1 on Mac and Syncthing-Fork 1.27.2.1 on GrapheneOS.

I’m syncing a folder that has over 8000 files in it.

Initially the sync was going “fast”, with multiple megabytes/second (still slow for LAN speeds), but now it is going at a crawl at 95% done, around 96.6 KiB/s (or less, it seems like sometimes there are periods of 0KiB/s).

I’ve even disabled fsync for this folder per some of the other forum threads, and it has had absolutely zero effect on the sync performance.

Why is this happening?

The performance should remain high through the entire sync instead of going to a crawl.

[tomasz86]

Are you trying to sync a single folder with 8000 files from the Mac to Android? If yes, then this is going to be extremely slow. There is really nothing that can be done about it (see https://forum.syncthing.net/t/how-to-deal-with-abysmal-i-o-performance-on-android-10/18406 for some details).

[macsync (Mac)]

Yes syncing between Mac and Android, using Android 14.

So it’s just some mystery with Android and nothing can be done?

That’s really sad to hear.

[tomasz86]

Yeah, unfortunately, it’s just about the sheer number of files. The size doesn’t matter, i.e. they can be 0 byte sized and it will still take a very long time to sync them. In my testing, what was a matter of seconds or maybe a few minutes on older Android versions, now takes at least a few hours .

[taoeffect]

Thanks @tomasz86 and @macsync for describing this issue. I also was running into this same issue and asked the GrapheneOS developers why they thought this might be happening, and here is what they had to say.