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Re: SCP file transfer speed



Stephan <stephanwib%googlemail.com@localhost> writes:

> I performed a quick benchmark with netio and it showed up the best
> possible speed on TCP.
>
> NETIO - Network Throughput Benchmark, Version 1.26
> (C) 1997-2005 Kai Uwe Rommel
>
> TCP connection established.
> Packet size  1k bytes:  11506 KByte/s Tx,  11116 KByte/s Rx.
> Packet size  2k bytes:  11512 KByte/s Tx,  11469 KByte/s Rx.
> Packet size  4k bytes:  11513 KByte/s Tx,  11469 KByte/s Rx.
> Packet size  8k bytes:  11513 KByte/s Tx,  11100 KByte/s Rx.
> Packet size 16k bytes:  11513 KByte/s Tx,  11469 KByte/s Rx.
> Packet size 32k bytes:  11513 KByte/s Tx,  11470 KByte/s Rx.
> Done.

That looks good; 91.7 Mb/s and I dimly recall 93 as max theoretically
possible with framing, IP, TCP headers.

> UDP, however, does not work out of the box. It continuously displays
> these errors:
>
> sendto(): No buffer space available

Well, that's not really not working.  A modern cpu can call sendto()
faster than the interface can send packets, and without any sort of flow
control or congestion control, any buffer will be overwhelmed.  But as
you say it's not relevant.

> During an (uncompressed) scp copy, CPU usage on the receiver side is
> largely below 10 % and disk utilization about 50% (which makes me
> wonder because this disk can make about 100MB/s on sequential
> write). I can copy to other Linux and Solaris boxes in this network
> with about 10 - 11 MB/s from the NetBSD boxes - just receiving is
> slow.

Is it just one NetBSD box that is slow?  How many did you try?
Do you have wapbl enabled?  Which fs?

Try copying to /dev/null instead, to take the disk out of the experiment.
I just copied to the disk (I had used /dev/null before) on one of my
normal machines, and still got 10 MB/s.

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