rsync feature request: conditional compression

Seann Herdejurgen seann at
Thu Jan 16 00:48:00 EST 2003

rsync is optimized to conserve network resources, sometimes at the expense of CPU resources.  As
long as CPU's are fast and networks are slow, rsync with compression
does a great job.  However, if I run rsync on a slow box (166MHz Ultra SPARC) over a fast network
(100Mb/s), the compression kills the transfer rate.  I turned compression off and I should be done
rsyncing my files (60GB) overnight.

I would like to request a feature I call "conditional compression".  What this would do would check
the network buffer, and if it is mostly full, then rsync knows that the network is slow and it will
compress data.  If the network buffer is mostly empty, then rsync knows that the network is fast and
doesn't waste time compressing data.  I use the terms "mostly full" and "mostly empty" loosely.  It
could mean 85% full and 15% full; without testing, I don't know which values would work best.  This
algorithm would be self-adjusting to both network and CPU load.  I haven't thought through the
ramifications of the impact on the remote rsync process, but I suspect they will have some impact on
the overall performance.

Since I am writing to this list, I wanted to take a few words to thank you guys for a great piece of
software.  I have been using it extensively for the past year, and it solves a good number of
problems I have.  I have been using it for the past 6 months for making rotating snapshot backups of
my home Linux server.  In case you are interested in the implementation, click here:

Since I am not a member of this mailing list, please contact me directly via e-mail.

Seann Herdejurgen
seann at

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