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Re: [LUG] Rsync compression vs link speed

 

Simon Williams wrote:
> I'm in the process of reorganising my backup system, and was wondering 
> if anyone had any thoughts on how effective rsync's -z (compression) 
> option is on fast links (100Mbps ethernet).
> 
> There must come a point when compressing the data takes longer than it 
> would to just send it over the link as is- the question is what ratio of 
> processor speed to link speed would this happen at?

It would likely also depend on how compressible the differences are.

If the difference between backup runs is files have been padded with a
long stream of short repeating sequences (think vast chunks of the human
genome), then it will almost always be cost effective to compress this
at some point.

That said rsync was written on the assumption the link would be low
bandwidth, high latency, neither of which apply on a modern LAN. The
word on the street is compression is counter productive on LANs, but I
assume it is easy enough to test this.

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