Rsync's Speed

[Jerry Seutter]

See below.

On Thu, Jan 22, 2004 at 12:42:44PM -0800, jw schultz wrote:
> On Thu, Jan 22, 2004 at 01:36:05PM -0700, Steve Sills wrote:
> > Well, it is running under SSH, that could slow it down i guess....
> 
> Very easy to tell.  If ssh is burning user-mode cpu time the
> encryption is a factor.
> 
> It is very unlikely the encryption is having any affect on
> throughput.  Unless you are on very old hardware the network
> is slower than the CPU and for rsync the disk latency likely
> makes it slower than the 10MBps network.

I will have to disagree with you on this point.  It depends on your
definition of old hardware, I guess.  I did some testing with a 
400 MHz machine and found that it was able to transfer via ssh 
at a rate of about 1.4 Megabytes/sec.  That was with the default
cipher, which was... uh... 3DES?  Extrapolating linearly, you 
would need about 2.8 GHz to fill a 10 Megabyte/sec (100 megabit)
connection.  This is assuming my machine is a typical 400MHz
machine.

In my situation I found that changing to the arcfour cipher (now
considered weak encryption) increased throughput to 2.7 Megabytes/sec.
For a secure but middle-speed cipher you can also try blowfish.

Jerry Seutter