[Beowulf] Re: switching capacity terminology confusion

Nifty Tom Mitchell niftyompi at niftyegg.com
Sat Sep 19 19:58:28 EDT 2009


On Fri, Sep 18, 2009 at 07:11:41AM -0500, Rahul Nabar wrote:
> On Thu, Sep 17, 2009 at 10:58 PM, Gerry Creager <gerry.creager at tamu.edu> wrote:
> >
> > With the POSSIBLE exception of the newer Nexus line from Cisco, I can't
> > think of a reason I'd put a Cisco-labeled switch in my data center... except
> > for a Linksys for non-critical applications.
> 
> 
> Nexus is expensive though! They tell me that it approaches latencies
> of Infiniband and is close to the operations of a lossless switch.
> That's what I got from their sales guy. But again, we weren't ready to
> pay the premium.

I suspect one important point is the difference between data center
needs and some types of Beowulf cluster needs.

Today a data center needs lots of management bells and whistles while a
cluster locally needs flat out packet switching and minimum management
overhead.  A modern business data closet is full of a tangled mix of
services and regulated activities that requires more than just data
switching.  In this regard Cisco (and others too) has some very valuable
product offerings.

A small but full feature switch can act as the gate keeper filtering packets
interfacing to the Internet, campus and routing services.  In some
cases it can also provide audit that net Nannie policy may require.
i.e. it is part of the campus IT service foundation.

The cluster itself needs very little in the way of special services and can be
setup and managed as a homogeneous soft gooey center with a hard crusty
outside.   A "simple" but fast switch with enough ports seems sufficient.
NFS traffic (fast cascading funnel tree) can be different than say MPI traffic
with all hosts communicating at the same time with all the neighbors (one big cross bar).
Your cluster design may well shape your switch benchmark testing.

A quick look at Nexus data sheets tells me that you are paying
for future expansion.  The chassis behind the cards is fast, very fast.

Heck call Cisco and ask for an evaluation sample, or evaluation discount. ;-)

-- 
	T o m  M i t c h e l l 
	Found me a new hat, now what?

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