2-machine cluster setup

[Josip Loncaric]

dan stanescu wrote:
> 
> Hi,
> 
> we're wondering if anyone can give us an advice re. the SAN
> for a 2-node beowulf. Since no switch/hub is necessary,
> I thought only one cross-over Ethernet cable would be
> enough. I saw however that some vendors use two cross-over cables,
> with 2 NICs per node only for the SAN. I wonder what the benefits
> of that would be?

A single crossover cable would work nicely -- you'll get a direct full
duplex connection.  Double connection (and using Ethernet bonding) would
give you almost twice the bandwidth but still the same latency.  More
bandwidth is nice, but there is little benefit in doubling the bandwidth
if your limitation is latency.  Know your code's bottlenecks, and act
accordingly.  If you are uncertain, start with one connection, measure,
then add the second connection if needed.  Then again, Fast Ethernet
cards are cheap (e.g. NetGear FA310TX was $11.95 each at buy.com
recently).  Adding two FA310TX cards and a crossover cable should cost
under $40 including shipping (in the USA).  Not bad, although you would
need a driver update to get full performance.

Sincerely,
Josip

-- 
Dr. Josip Loncaric, Senior Staff Scientist        mailto:josip@icase.edu
ICASE, Mail Stop 132C                       http://www.icase.edu/~josip/
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