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:


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

Values for "-c", as far as I know, are:  blowfish|3des|des
(This is from OpenSSH 3.7.1)

	Best regards,


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