[ILUG] Dump very slow across gigabit network

[Jimmy Tang]

On Fri, Sep 14, 2007 at 03:22:30PM +0100, chris at darach.ie wrote:
> On Fri, Sep 14, 2007 at 12:09:35AM +0100, Conor Daly wrote:
> > I'm using dump to backup a number of filesystems to a tape hosted on a
> > remote machine.  The machine being backed up is still in commissioning so
> > it hasn't got its full complement of data yet.  Last night, one 300Gb
> > filesystem had about 21Gb used.  It took 3.5 hours to dump at an average
> > rate of 1530 kB/s (according to dump).  By my calculations, if this
> > filesystem fill completely, it will take 57 hours to backup.
> >  
> > The dump runs like this:
> >  
> > Remote machine mounts the tape
> > local machine does:
> >  
> > export RSH=ssh
> 
> Erm - isn't ssh chronically braindead when it comes to using it
> for this purpose ? 
> From
> http://www.sunmanagers.org/pipermail/summaries/2003-March/003345.html
> 
> "
> > The problem is that using rsh, the transfer rate is around
> > 3,000KB/sec,
> > using ssh its only around 600KB/sec.
> "
> 
> Doesn't SSH still have that internal 2k block limit ?
> 

try these patches out for openssh to get better performance over
highspeed links. 

http://www.psc.edu/networking/projects/hpn-ssh/

though i think the more recent versions of openssh have some dynamic
code to scale the block limits.

also wouldn't the number of small files be a factor in how fast you can
read the files (number of file opens and closes). I guess if you're
dumping the filesystem it shouldnt really matter.

Jimmy.

-- 
Jimmy Tang
Trinity Centre for High Performance Computing,
Lloyd Building, Trinity College Dublin, Dublin 2, Ireland.
http://www.tchpc.tcd.ie/ | http://www.tchpc.tcd.ie/~jtang