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Subject: Re: [OMPI users] switch and NIC performance (was: very bad parallelscaling of vasp using openmpi)
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-09-23 15:15:55


Wow; I should point out an amazing coincidence here. Doug Eadline
used [almost] exactly the same analogy that I did (truck vs. F1) in a
column that was published today in Linux Magazine:

         http://www.linux-mag.com/id/7534

I swear I didn't read his column before I posted my answer this morning!

:-)

On Sep 23, 2009, at 10:38 AM, Jeff Squyres (jsquyres) wrote:

> On Sep 23, 2009, at 10:15 AM, Dave Love wrote:
>
> >> So, how does one go about selecting a good switch? "The most
> >> expensive
> >> the better" is somewhat a unsatisfying option!
> >
> > Also it's apparently not always right
>
> +1 on Dave's and Joe's comments.
>
> For example, not all of Cisco's switches are suitable for "ultra" HPC
> clusters. Cisco has some very expensive switches whose goals are very
> definitely not the same as what ultra HPC clusters typically need.
> They're great switches (ok, I'm a bit biased ;-) ), but they're not
> what you would need for an ultra HPC cluster. Buying one of these
> would be kind of like buying an F-350 truck instead of an F1 formula
> race car; both are excellent at their respective tasks, but they're
> very different tasks.
>
> My point: a network switch != a network switch != a network switch.
> Make sure you understand what workloads and tasks the network switch
> was designed for; don't just rely on published spec numbers -- they
> don't tell the full story. Both an F1 and an F-350 can go 100 mph --
> but they get there in very different ways.
>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>

-- 
Jeff Squyres
jsquyres_at_[hidden]