[Beowulf] MPICH "remote access" speed

[Craig Tierney]

On Sun, 2004-11-28 at 20:19, steve_heaton at ozemail.com.au wrote:
> G'day all
> 
> Another newbie question for which I beg your tolerence.
> 
> I'm money poor but time rich. Given the limitations of my hardware (4x dual P3 nodes, GigaEther switched interconnect) I'd like to tweak the cluster's performance as much as possible :)
> 
> I was wondering if anyone has put RSH v's SSH head-to-head under MPICH in terms of performance?

SSH can be slower when there is alot of ascii output from
the processes which ssh has to encrypt/decrypt.  SSH does
start a bit slower, but that is only a startup issue.
SSH scale better on larger clusters because it can be configured
not to use privileged ports.

You can investigate other starting mechanisms like those MPD
or what MPICH2 uses.  

Since you are "time rich", how about you configure MPICH to
use both, do a study, and let us know the definitive answer? :-)

Craig

> 
> I've read in a few places that SSH is a bit slower due to the need to exchange keys etc. On the other hand I hear that some applications can leave the connection open under SSH and that can make them faster than having to RSH for every exchange.
> 
> As always, thoughts, comments etc greatly appreciated :)
> 
> Cheers
> Steve
> 
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> 
> 
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