Mailing List Archive

[Bug 2888] Consider adding other compression schemes (lz4, zstd)
https://bugzilla.mindrot.org/show_bug.cgi?id=2888

Scott Baker <scott@perturb.org> changed:

What |Removed |Added
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CC| |scott@perturb.org

--- Comment #2 from Scott Baker <scott@perturb.org> ---
I came here to request alternate compression methods, and found someone
had beat me to it. Consider this my +1

Currently OpenSSH only supports GZIP compression which has speed
constraints on modern CPUs. Enabling compression on file transfers over
a gigabit link actually increases the amount of time taken to transfer
large files due to the limitations of GZIP.

Please consider adding support for alternate compression methods. LZ4
and ZSTD would be excellent choices.

Even better would be support for external compression methods like
`tar` does with `-I`. That way in the future if new/better compression
algorithms are found SSH will automatically be able to utilize them.

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[Bug 2888] Consider adding other compression schemes (lz4, zstd) [ In reply to ]
https://bugzilla.mindrot.org/show_bug.cgi?id=2888

--- Comment #3 from Scott Baker <scott@perturb.org> ---
Transferring a 1.8GB VM image on a gigabit network:

```
root@green(~)
:time scp test.bin yellow:/dev/null
test.bin 100% 1821MB 108.0MB/s 00:16

# Enabling compression is significantly slower
root@green(~)
:time scp -C test.bin yellow:/dev/null
test.bin 100% 1821MB 20.0MB/s 01:30
```

Alternately using this "hack" with `cat`, `ssh`, and ZSTD I was able to
decrease transfer time by ~40%.

```
root@green(~)
:time cat test.bin | zstd | ssh yellow 'zstd - -d > /dev/null'

real 0m9.691s
user 0m12.178s
sys 0m4.458s
```

For transferring large files, and/or groups of large files via
scp/rsync having a modern compression method would be a **huge** win.

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