About rsync over SSH and compression

Darren Tucker dtucker at dtucker.net
Wed Jun 26 08:04:44 AEST 2019

On Wed, 26 Jun 2019 at 02:50, JCA <1.41421 at gmail.com> wrote:
> Thanks; I did not think of that. I have just run a few basic tests with
> both rsync and OpenSSH in their default settings, when it comes to
> compression. SSH compression seems to have a very slight edge.

OpenSSH does not allow you to set the zlib compression level for SSH2
(the protocol spec does not have a mechanism for doing so, although
it'd be possible to add it as a non-standard hack) and OpenSSH
hardcodes it to 6.  In rsync you can crank it up to --compress-level=9
which I'd expect to make it beat any theoretical advantage SSH might
have on compressible data, plus it can be smarter about skipping
already-compressed file types.

That said, I'll second what Stuart said that what matters is what
works best for your data set and environment.

Darren Tucker (dtucker at dtucker.net)
GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860  37F4 9357 ECEF 11EA A6FA (new)
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

More information about the openssh-unix-dev mailing list