SyncThing slow with numerous files?

I try to backup a 10GB send-only folder from my (Fedora) Linux laptop to a receive-only folder on my (GrapheneOS) Android phone.

The transfer speed is very slow. It’s been running for 20 hours now, and it is still not finished. It averages to 100 kB/s.

Initially, when I noticed how slow it is, I tried to change the pulling order from “random” to “largest first”. The transfer speed then increased to 10 MB/s until it dropped down again to 100 kB/s, when it reached the so-called “smallest files”. Now it is blocked at 98%.

Is SyncThing transfer speed limited by design with this setup?

Welcome here!

No it is not.

The storage in your phone is most likely the limiting factor. Search the forum and your will find several threads about this. :slight_smile:

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You mean it is a hardware or a software limitation of the Android storage?

Because I use a Google Pixel 8 with GrapheneOS, I consider it to be a standard setup and I expected to find an easy solution for that on this forum.

If it is an inherent limitation of Android, it means SyncThing can’t be used with mobile devices (except for a trivial backup need of a few hundreds of files).

I found those two other topics with no solutions:

As an experiment to replicate the issue:

  1. copy your Android internal storage over MTP to a folder on your PC.
  2. Try to sync it back from your PC to a folder on your Android phone with SyncThing.

The MTP transfer will take a few hours at most depending on the size of your Android internal storage, it can be just 15 min too if it is small.

But the SyncThing way will take many days or weeks.

This is a limitation of Android with no workaround (see https://forum.syncthing.net/t/how-to-deal-with-abysmal-i-o-performance-on-android-10/18406).

You can still use Syncthing on Android perfectly fine, just not with thousands of files located in a single folder, or otherwise you should be prepared for the slowness.

The common use case is to sync photos and videos, so most people never encounter this problem.