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Subject: Re: [OMPI users] very bad parallel scaling of vasp using openmpi
From: Peter Kjellstrom (cap_at_[hidden])
Date: 2009-09-23 12:56:11


On Wednesday 23 September 2009, Rahul Nabar wrote:
> On Tue, Aug 18, 2009 at 5:28 PM, Gerry Creager <gerry.creager_at_[hidden]>
wrote:
> > Most of that bandwidth is in marketing...  Sorry, but it's not a high
> > performance switch.
>
> Well, how does one figure out what exactly is a "hih performance
> switch"?

IMHO 1G Ethernet won't be enough ("high performance" or not). Get yourself
some cheap IB HCAs and a switch. The only chance you have with Ethernet is to
run some sort of bypass proto (OpenMX etc.) and tune your NICs.

/Peter

> I've found this an exceedingly hard task. Like the OP posted
> the Dell 6248 is rated to give more than a fully subscribed backbone
> capacity. Nor I do not know any good third party test lab nor do I
> know any switch load testing benchmarks that'd take a switch through
> its paces.
>
> So, how does one go about selecting a good switch? "The most expensive
> the better" is somewhat a unsatisfying option!