Where is my bottleneck?
Cedric Puddy
cedric at cadence.thinkers.org
Thu Mar 11 16:30:37 GMT 2004
On Thu, 11 Mar 2004, Marc Abel wrote:
> Thanks to all three for your kindness. Invoked as:
>
> rsync -lave ssh --delete --delete-excluded \
> --exclude ".[!.]*" \
> /home/me me at majority:composite_bu
>
> I did some looking around, and it seems like I haven't even installed
> the daemons for rsh, telnet, etc. (I'll follow up on this, but I can't
> this morning.) Likewise, running the straight rsync-to-rsync connection
> is proving to need a little studying up.
>
> I really did mean to say 2 Mbit/s. About 10 Mbyte/min is all that I'm
> getting. I can understand ssh slowing things down a lot, but not
> without seeing it get a lot of CPU time. These are 1 GHz machines,
> roughly, and they aren't getting slowed down.
There is an interesting note on SSH cryptographic speeds here:
http://lists.samba.org/archive/distcc/2002q3/000229.html
It shows how to get a benchmark on how quickly the different cyphers
perform, and between that, and sending a known amount of data over
an SSH channel, you should be able to quickly discover if a different
cypher might make a difference.
Here's something that might help to roughly benchmark SSH "raw"
with different cyphers:
---------------
bash-2.05b$ time cat /path_to_big_sample_file | \
ssh -c blowfish cadence.thinkers.org "cat - > /tmp/ssh_test_out"
real 0m1.126s
user 0m0.074s
sys 0m0.025s
bash-2.05b$
----------------
Values for "-c", as far as I know, are: blowfish|3des|des
(This is from OpenSSH 3.7.1)
Best regards,
-Cedric
-
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