[Gllug] Connecting a second Ethernet link (1 Gbps) between two servers

[John Hearns]

On Sun, 2008-01-20 at 19:45 +0000, John Hearns wrote:

> Emerges from cave. Scratches, adjusts fur clothing.
> "Uggg, uggg, uggg /etc/hosts Ugg."

Actually, I shouldn't joke.
Allocating a separate network, and subnet, on eth1 is a common technique
for high performance Bewoulf type clusters.
You connect eth1 to a separate set of switches, to get the maximum
performance for message passing traffic.
The names for the eth1 interfaces are generally put into the /etc/hosts
and are based on the names for the eth0 interfaces.
So, when your batch system allocates you a set of computers to run a
parallel job you have a pre-processing script which munges the hostnames
(say by adding -1' to them) and passes this argument to your mpirun
command.



In actual fact, we don't do this, though we commonly spec the separate
set of ethernet switches, as we install an MPI implementation which
works over UDP, and doesn't depend on the IP address.


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