Extremely slow file transfers (AGAIN)

Hi All,

I know this has been discussed several times in the FAQ and forums; but I’ve combed through the posts and can’t seem to fix my problem.

  1. I have a fast connection (100mbps down 10mbps up). I checked it with iperf and scp from the two machines in question.

  2. The address of the remote is showing as w.x.y.z:22000 (so I’m assuming no relay is being used)

  3. Ports 22000 (tcp) and 21027 (udp) are open on both machines and iftop shows traffic on both ports.

I have a large default folder (30G, many small files), and a few other smaller folders which add up to 20G. For the initial sync the smaller folders finished at the expected rate. The default folder took many hours, and was transferring at kbps speeds. (I restarted syncthing, connected multiple nodes, even some on the LAN, but no luck)

After the initial sync, I put in a 100mb file and it synced at roughly the right transfer rate (80mbps).

Any idea what might be the problem? (Admittedly it looks like a moot point for me now; since after the first sync completed it’s fast. But the next time I add a new device…)

Thanks in advance,


The connection won’t be the bottleneck in that case. This is most likely I/O bound.

That’s very strange. Both machines have new SSDs with 400mb/sec IO speeds (measured by hdparm -tT). Dropping to kbps speeds is a factor of 1000 off…

You’re right though. I just did a test: generated 1.5GB of files that are 1mb or less. It is doing about 15 or 20 files a second; it should be doing 70 or 80 (based on net speeds)…

Any idea how to improve this?

Start here: Configuration Tuning — Syncthing documentation

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I suggest testing the Network’s throughput between the two machines using iperf.

Iperf is a tool designed exclusively for testing the bandwidth between two computers it has clients available for Windows Android and Linux at the least there is a version 2 and a version 3 so you need to make sure you use the same version on both nodes.

You tell One node to be the server and the other to be the client and then you can run it in the opposite direction as well.

This will give you a benchmark for how fast the network connection is between those two nodes and whether there is a problem aside from syncthing or not.

It is a free utility that on Linux you can install from your distribution package manager and if you search Google you can find one for Windows.

You can start here:

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