[Beowulf] How to configure a cluster network

Patrick Geoffray patrick at myri.com
Thu Jul 24 19:02:11 EDT 2008


Hi Mark,

Mark Hahn wrote:
>> With any network you need to avoid like the plauge any kind of loop,
>> they can cause weird problems and are pretty much unnessasary. for
> 
> well, I don't think that's true - the most I'd say is that given

It is kind of true for wormhole switches, you can deadlock if you have 
loops (direct of indirect). The subnet manager / mapper will often prune 
some loopy links to be able to generate deadlock-free routes in 
polynomial time. So, you could have links that are just not used by any 
routes in funky topologies. Ethernet spanning tree is the most extreme 
paranoia, it will always prune all links but one between 2 switches 
(modulo link aggregation).

Patrick
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