[Beowulf] How to configure a cluster network

Nifty niftyompi Mitch niftyompi at niftyegg.com
Fri Jul 25 13:52:18 EDT 2008


On Thu, Jul 24, 2008 at 06:39:00PM -0400, Mark Hahn wrote:
> 
>> If you  need 144 ports a single switch will be be more cost effective
>
> you'd think so - larger switches let you factor out lots of separate
> little power supplies, etc.  not to mention transforming lots of cables
> into compact, reliable, cheap backplanes.  but I haven't seen chassis
> switches actually wind up cheaper.
>
> of course, IB hardware prices seem to be extremely fuzzy (heavily  
> discounted from list).
>
>> than a gaggle of 24 ports gathered together into a tangled hairy cable ball with
>> 144 ports exposed.
>
> once very nice thing about the leaf/trunk fat-tree approach is that your
> switches can be distributed in node racks.  so any individual rack has a 
> fairly managable bundle of cables coming out of it.

Good point.  And with double data rate links (QDR some day) the reach of a DDR cable is
shorter so yes distributing smaller switches in a set of racks can help in another way.

Optical links may bring things back toward larger switches.

In some cases updating the set of core switches to DDR and leaving the 
outer switches at SDR can improve cross sectional bandwidth. 

Also for upgrades to DDR smaller switches deployed some now some later
lowers the budget burn rate.

All good stuff.


-- 
	T o m  M i t c h e l l 
	Looking for a place to hang my hat.

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