RSH scaling problems...

Daniel Kidger Daniel.Kidger at
Tue Dec 17 09:58:11 PST 2002

>> > ssh has a mode in which it can use a high port. That's how the
>> > 370-node FSL system did it in 1999. This technique also worked OK on
>> > Cplant at 1200 nodes.
>> Greg,
>>    Our users who have tested ssh have told us that the wall clock
>> time is much larger than if they use rsh (I'm sorry I don't have any
>> numbers :) This are MPI jobs running over about 12-24 hours.
>> Have you seen this?
>I haven't seen it. If your jobs run that long, just about any method
>of starting will be efficient enough to not increase the runtime.

Dont forget that by default ssh encripts all traffic.
If you have a lot of stdout then this will slow things down I guess.

There are options to ssh to change or turn off this encription.


Dr. Dan Kidger, Quadrics Ltd.      daniel.kidger at
One Bridewell St., Bristol, BS1 2AA, UK         0117 915 5505
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