Really slow Wifi over SCP

Hi everyone,

When I send a file via SCP from Ubuntu to OSMC, my speeds start at around 2.5 mb/s, then drop down to 500kb/s and more or less stays there.

I though the problem was my Wifi - a Realtek dongle. I have replaced that with a Ralink dongle that has an antenna.

That made zero difference - still starts at 2.5mb and slows to 500kb.

Any ideas?


Have you checked your CPU utilization while doing the transfer? SCP encryption is quite tough on the CPU and the small device is not made for this.

Tested over ethernet?

The CPU is running high. So that is probably it.

Is there a way to make unencrypted transfers? Alternatively I can replace it with the Pi 2.

Do you have a Pi 1 or Pi 2 ?

The CPU in the Pi 1 is very slow so sending a file encrypted with something like SCP will be somewhat slow. Is it any faster if you install the FTP server and upload it using that ? (EG an unencrypted transfer)

Also are you trying to save the file to the SD card ? Some SD cards have really poor write performance - 2.5MB/sec would be typical write performance of some of the slower cards. It may start out faster while it is being buffered but once the buffer fills it will slow down.

You might find a different SD card faster.

I’m writing to a hard drive, but I suspect the CPU is the bottleneck. I will try FTP and if that fails, buy a Pi 2. Thank you!

use samba for transfers ?

scp is always slower than ftp…Use ftp instead

Thanks for all the help. FTP is a tad faster, but I think it’s the Pi’s CPU. I’ll get a Pi 2 at some point and hopefully that will solve it.

The network performance of the Pi 1 is definitely CPU bound - even on Ethernet it can only just manage about 95Mbps when the CPU is otherwise completely idle. If the CPU is also busy doing something else such as running Kodi, network performance plummets to only half that at most.

The Pi 2 has a much faster CPU and consequently can achieve much better network performance when the system is under load, and the network speeds don’t really fall much if at all.