Re: rsync very slow, but not a network issue

[Thorsten Kampe <thorsten at thorstenkampe dot de>]

* Alexis Gallagher (2004-07-12 19:46 +0200)
> I am finding that rsync+ssh is giving extremely slow file transfers. But 
> this slowdown is hitting not when it needs to send data over the 
> network, but when it applies the rsync algorithm which is supposed to be 
> faster than sending all the data over the network. This is very puzzling.
> 
> For a benchmark, I tried transfering a 5.4 MB mp3 file three different 
> ways. Here were my results, as reported by 'scp -v' and 'rsync 
> --progress --stats':
> 
>     scp: 311000 B/s
>     rsync (file not there): 309000 B/s
>     rsync (file already there): 741 B/s
> 
> When the file is alredy there, rsync reports a speedup of about 70. 
> (When the file is not already there, the speed up is 1, of course.) I am 
> running rsync over ssh with pre-generated keys installed in my .ssh 
> directories.

rsync under Cygwin is extremly slow and CPU intensive. For example a
simple script that syncs my dot files from my local NetWare server
takes 1:10 minutes to run and eats about 60% CPU while on my Gentoo
box (which has exactly the same hardware) it takes 7 seconds and 2%
CPU.

Try disabling checksumming, zipping and transfer the whole file
('-W'). Try it without ssh.

Thorsten


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