On Sun, 2018-09-02 at 22:16 -0600, Chris Murphy wrote:
Fedora 28 Server
Fedora 28 Workstation
dd-wrt 802.11n Broadcom based router
Connected wirelessly 5GHz, wired ethernet cable is physically
disconnected from Server
File transfer from Workstation to Server
scp: scp itself reports ~620KB/s; where nload on the server reports
~4.9Mbit/s
smb: GNOME reports 4.9MB/s; where nload on the server reports
~39.8Mbit/s
Why? That's rather unexpected.
Command is
scp test.bin f28s.local:/srv/scratch
Using nc, I get speeds slightly faster than smb. OK so encryption? If
I connect wired, and then 'nmcli c down <ID>' to disconnect the
wireless connection:
scp: 12MB/s, nload ~101Mbit/s
smb: nload ~96Mbit/s
Sooooo, it's not encryption. Why would scp be this much slower only
with a wireless connection? And using:
rync -avzhe ssh test.bin f28s.local:/srv/scratch
Over wireless, this is just as bad as scp.
SCP protocol is really slow, especially on networks with high latency
(wireless). The reason why is mostly the size of buffers, which is very
small and SCP waits for every part to be confirmed by the remote host
before sending another part.
You can google "scp speed" and you will get a lot of answers, sometimes
wrongly accusing the encryption or the compression, but really, the RTT
and buffers are the fault as I write here:
https://superuser.com/a/1101203/466930
SCP should be really used only as fast hack for copying files in fast
local networks. For all other cases, use SFTP or rsync if you need
something more complex.
Regards,
--
Jakub Jelen
Software Engineer
Security Technologies
Red Hat, Inc.