bandwidth issue

Ryan Malayter malayter at
Wed Mar 11 14:02:29 GMT 2009

On Wed, Mar 11, 2009 at 7:41 AM, Gero  Pflanz <Gero.Pflanz at> wrote:
> Is it sufficient to change only those 2 parameters ?
> Will this also change the buffersize af the other host (via rsync
> communication)? In the logs I do not get any information that
> the sockopts parameter is changing something (although I am using
> "vvvv").

You should change the buffer sizes on both ends of the connection in
my experience if you are running one side in daemon mode. If you are
running over an SSH tunnel, there may be additional complications, and
some tweaking might need to be done at the SSH layer.
At 190 ms, you need this window size:
  6 Mb/s * 0.190 s = 1140000 bits = 142500 bytes

This value is greater than 64KB, would require the use of TCP windows
scaling options. Most recent OS (even windows) support this TCP window
scaling automatically, but I have seen some ill-behaved firwealls,
IDS, VPN gateways, and other network devices that choke on TCP
connections with the windows scaling options set. All you can do is
try to see if such a device is in your path.

Note that if your rsync proccess is CPU or disk bound, these settings
will not help. Try lowering the compression level or using the
whole-file option if that is the case.


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