[ILUG] slow ssh compression performance

[Paul Mc Auley]

On Wed, 12 Oct 2005 08:28:10 +0100  David Malone wrote:

| The suggestion that it may be buffer related is also worth following
| up. If I understand right, The folks that use SSH in a high-performance
| environment have discovered that there buffers inside SSH that have
| the same effect of limiting the TCP window size to some small value,
| which makes it hard to transfer data quickly when the round trip time
| is large. Compression might actually make this a little worse if the
| fixed buffer size is before rather than after compression.

It's also worth considering the fact that the results shown might not be 
considered a problem.

A. There is a specific case where I'm able to transfer a lot of empty data 
   faster by compressing it before handing it to ssh.
B. You should probably do it that way then.

I suspect that if ssh was tweaked to favour large file transfers, its 
performance as an interactive shell could be impaired.

As a general rule I tend to prefer to use tar over ssh to transfer 
non-trivial numbers of files, I suppose this makes the case for ensuring 
that tar adds gzip to the chain too.
	Paul