sync speed is decreasing over hours..

Support
1

dear all,

I would like to ask, why my sync speed is decreasing over hours… refeering to “Why is synchronization between two devices so slow?” and “FAQ — Syncthing documentation” I did not find a hint…

I sync from MAC (M2, 32 Gig) to a raspberry Pi 5 (8 Gig). after some hours, the speed goes down from (just now as example) “2,21 MiB/s (3,1 GiB)” to at about 200…500K. When I restart both sides via WEB-insterface, the speed immediately goes up again to previous level.

Background: on both sides the disks are USB-3-connected. Connection between the 2 computers is WLAN.

versions raspberryPi: syncthing v1.27.3, Linux (64-bit ARM)

  • OS “Debian GNU/Linux 12 (bookworm)”
  • HW Raspberry Pi 5 Model B Rev 1.0

MAC: syncthing v1.27.2, macOS (64-bit ARM)

  • OS Ventura, 13.6.4
  • HW Apple M2 Pro

history on “raspi-side” I recently switched from raspi 4B → raspi 5 (see above). because of many files (~2…3 TB) I keept the files on “raspi-side” and now (try to) re-sync …

any ideas, hints? thanks in advance jürgen

2

I have heard this but not seen it nailed down. Taking CPU, block and heap profiles before and after might be helpful.

3

Also watch out for the CPU temperature on the raspi. If heavy hashing or encryption is involved, it might be throttling down because it gets hotter by the minute.

2 Likes
4

The SD card of the pi might also throttle. I know you’re syncing to an USB3 drive, but syncthings database is most likely still on your rootfs.

5

I think, you’re right … it might be NOT a syncthing problem…

(I forgot to mention: I boot the raspi from usb disk, data is on a different disk, not the same, so hopefully the SD-card should not be involved in my case …)

temperatur: values : (last 2 days)

  • 54.3°C … 67.5°C
  • 55.4°C … 68.6°C

→ might this be a problem? (I did not find reliable values for “too high” temperatures… found somthing ~80°C, but from my point of view -gut feeling- thats MUCH too high … what do you think?

– I stopped syncthing and tried to transfer my data from mac to raspi via “rsync -av…”.

→ I found the same reaction: it started quickly, slowed down over night… so it could be a “local raspi-problen”

6

Depends on if those numbers are when the system is fully loaded or when the system is idle.

Is there any active cooling in your RPi 5 rig?

At least a few of the past Raspberry Pi models (including the RPi 5) have thermal CPU throttling with two thresholds at 80°C and 85°C.

What’s the capacity of the power supply for the RPi?

Is the USB drive holding the data self-powered or has an external power supply?

7

the power suppply offers 27W, the usb sys-disks is directly, the data disks are connected via powered-usb hub.

8

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