While transferring large files (5GB+)to different geographical locations via internet we’ve noticed that transfers almost always start fast, and then begin to “settle” into a slow transfer rate of 1-4MB/s. If we restart syncthing on one side of the connection, it’ll reconnect and we’ll start seeing speeds hit near max (~70MB/s) for awhile, then it will slowly setting down back to the 1-4MB/s over the course of the next hour or so. This is consistent with several different sites and network providers, so while I’d chalked it up to some kind of network management on the part of our ISPs, I’m becoming less convinced of that, especially because I can now get a boost in speed on demand simply by restarting one instance. Some additional info:
1.) The sync devices are dedicated hardware, with the database on an m.2 drive and the data moving to a single SSD. Drive, RAM, and CPU utilization don’t appear to be the problem from what we can see. These are Windows based server devices.
2.) Network connections are typically 500Mbit up/down on both sides, with several being 1Gbit.
3.) The timeframe of how this problem presents is a challenge to troubleshooting. We can start a 500GB folder overnight, restart syncthing, and see it moving at 40-70MB/s. When check back in the morning 10-12 hours later, we’ll find it running at 1.8MB/s-4.7MB/s with 350GB left to transfer. If we restart, we can burn through another 50GB relatively quickly (inside of an hour) before it seems to fall back into the slower pattern.
Any idea what’s going on here?