[Beowulf] Cluster Diagram of 500 PC

Daniel Navas-Parejo Alonso danapa2000 at gmail.com
Thu Jul 12 17:41:11 EDT 2007


Drawback when stacking could be scalability (there is always a maximum
number of switches that could be stacked), but is a nice solution for a
limited number of nodes. Of course, this is not at all an HA approach.

There is a network manufacturer that implements a couple of protocols that
could be interesting for network redundancy and low-latency failover
mechanisms, that can perfectly fit on that ring proposal you're doing. Those
protocols are EAPSv2 (based in a set of rings) for L2 and ESRP for L3. Yet
once again, propietary protocols, that's the drawback.

Spanning tree has some caveats and could make you to increase the number of
hops when communicating two distant leafs. In this case there are some
vendor-specific spanning tree implementations (i.e PVST+, EMISTP, etc...)
but also a number of "standard" Spanning tree standard implementations (for
instance the first definition of STP in 802.1D and its successors 802.1w,
etc....)

Anyway, hop latency in Ethernet is most of times just peanuts in terms of
latency compared to TCP/IP stack overhead...

Other option could be not to impement redundancy but of course this depends
on the criticity of your cluster....




2007/7/11, Mark Hahn <hahn at mcmaster.ca>:
>
> >> my question is: do switches these days have smart protocols for mapping
> and
> >> routing in such a configuration?  I know that the original spanning
> >
> > That's 802.3ad. Quick pointer:
> > http://en.wikipedia.org/wiki/Link_aggregation
>
> I don't think that's what I meant.  imagine instead that you have
> 48pt GE switches, each of which has 4x 10G extra ports.  now, take
> 5 such switches and fully connect them (each switch has a 10G link
> to each of the other 4 switches).  I don't think 802.3ad helps here,
> since what you want is to _avoid_ a single spanning tree, which
> would necessarily have one root.
>
> 802.3ad is exactly the right thing if you simply want to stack
> two such switches and want 4x10Gb inter-switch bandwidth.
>
> I noticed that d-link appears to use 10G links for stacking, but
> has a route-discovery protocol that lets them structure the switches
> into a ring.  I'm not sure they use this to reduce hop-count, though -
> perhaps just for reliability.
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