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  1. I'm running speed tests on raspberypi 3 b+ (gigabit ethernet interface).

  2. I've tested with ethtool from the terminal, and it shows

    Speed: 1000Mb/s

Based on this result I assume both the router and the wire support 1000Mbps network transfer speeds.

  1. A HDD is connected to the pi. I've tested it, and found the average writing speed is about 60MB/s.

  2. The files I used in testing are at least 1GB, and my laptop supports gigabit ethernet.

When I transfer files from my laptop to the pi's HDD using WinSCP, the average speed is only around 11MB/s.

Even though the raspberry pi has USB2.0, the speed should be no less than 11MB/s. I think it should be at least 30MB/s or even 50MB/s.

I don't understand why the data isn't moving faster. Can someone explain why I'm getting these results?

Alxt
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2 Answers2

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There is an HDD connected to the pi. I've tested that the average writing speed of it is about 60MB/s.

This must mean the HDD is USB 3.0 capable, and that you did not do the tests on the Pi, because it is not possible to do 60 MB/s through a USB port on the Pi; the realistic limit of a 2.0 port is ~35 MB/s. But you are already aware of this.

Even though the raspberrypi only has USB2.0, the speed should be no less than 11MB/s. I thnik it should be at least 30MB/s

My experience is that would be an extreme upper bound at least on the Pi, and (even more realistically), expect a little over half that on average.

Which still makes 11 MB/s a little slow, but not outrageously so. My other observation from experience would be that using SSH encryption is a little slower than NFS with no encryption.

When I do use SSH, I almost always use sshfs, not scp. I've read casually that the latter is slower because of how it works, but I wouldn't assert that as fact -- you can do your own reading and tests if you are interested.

goldilocks
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As goldilocks has stated BOTH the HDD and Ethernet go through the USB2 Hub, which limits speed.

If you want faster transfers (on Pi3/Pi3B+) use the onboard WiFi, which bypasses the Hub. (FTP is also likely to be faster.)

Milliways
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