speed differences

uwp at dicke-aersche.de uwp at dicke-aersche.de
Tue Nov 12 22:42:00 EST 2002

Today, Mozzi wrote:

> In all test the same 2.5 Gig logfile was used for transfer
> (2719312019 Nov 12 11:42 maillog.back)
> (2.5G Nov 12 11:42 maillog.back)
> The transfer was done over two Gigabit nic's one onboard broadcom on
> IBM X440 server, Other Intel on standard selfbuilt dual P3 880 machine.
> Both servers are running Red-Hat Linux
> Coping from dual P3 800 3Gig ram Seagate Cheetha 10 000 rpm disk
> to dual P4 Xean mp 6Gig ram 6xdisks in raid5e

This sounds awfully fast ! :-)

> rsync -azSHve ssh maillog.back root at
> wrote 357110468 bytes read 36 bytes 308252.49 bytes/sec

Gigabit and only 308 KB/s ???

> rsync -pogve ssh maillog.back root at
> wrote 2719644062 bytes read 36 bytes 5136249.48 bytes/sec

This sounds better but for Gigabit even too slow. It's faster because
you're not using compression. Compression slows a fast channel down
but can speed up slow channels. I don't know if -S is really needed
but what could give you much better results is -e 'ssh -c arcfour'.
arcfour is at this time the fastest method for ssh encryption,
it's double as fast as 3des (which is default for ssh) and even faster
than blowfish. Too bad that there's no encryption none anymore. I really
like to have the authentication mechanisms of ssh but I don't need
encryption everywhere, especially on such occasions where you have
a private cable and just wasting time by using encryption.

BTW, not every switch can handle it, but Gigabit cards itself should
all use jumbo frames. On intel GBit cards you just have to set
ifconfig ethX mtu 9000 to switch jumbo frames on. I don't know
how to do it with broadcom cards. But with jumbo frames you should
get upto 15-18 MB/s (MB stands for MegaByte not MegaBit :-)).

I think for a simple crossed cable this should be an option for you.
Please tell us how it went, if you could speed things up.


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