compression, built-in or ssh ?
jw at pegasys.ws
Fri Oct 17 18:00:54 EST 2003
On Fri, Oct 17, 2003 at 09:34:17AM +0200, Lapo Luchini wrote:
> jw schultz wrote:
> >>What is the general recommendation for compression when using ssh?
> >Use rsync's compression.
> >>If so, is there a clear prefference which is more efficient, rsync or ssh?
> Why, if they both use zlib?
> Moreover compressing "at a higher level" always seems a good diea to me
> (e.g. if you compress the whole SSH session, you're sure *anything* is
> compressed, if yuo let each application encrypt you have to nkow each
> application, and maybe it does compress only data and not commands, just
> to do an example).
> In the case of rsync I always thought it was the same, and I never use
> -z on rsync as I have compression on by default on SSH connections.
> Any actual reason not to do that?
For the file data sent rsync seeds the compressor so that it
achieves a higher level of compression than can be achieved
my only compressing the blocks transmitted.
Whether you use the -z option or not rsync is
micro-optimised in transmitting the file list so that the
meta-data transmission is effectively compressed. About the
only thing compressible that is not compressed are error
Were it not for the micro-optimisation i would say that
which level to compress for maximum effect would depend on
the amount of non-matched data sent.
One way that doing the compression in ssh does have an
advantage is that with ssh protocol version 1 you can
control the compression level.
J.W. Schultz Pegasystems Technologies
email address: jw at pegasys.ws
Remember Cernan and Schmitt
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