[Beowulf] The move to gigabit - technical questions

Glen Gardner Glen.Gardner at verizon.net
Mon Mar 14 14:41:37 PST 2005

Gigabit will be a little faster than 100Mbit on a small cluster, but not 
a lot.

I ended up using 5 cheap gigabit switches to make a gigabit concentrator 
for my 12 node cluster.
It eliminated the tendency for the network to saturate under a heavy load.

It also let me use gigabit network cards in my I/O node and controlling 
node with a small improvement in file I/O.
The compute nodes remaind with 100 Mbit to conserve power. The setup 
works rather nicely.


Vincent Diepeveen wrote:

>Good evening,
>It's interesting to investigate what gigabit can do for small home clusters.
>Any latency oriented approach is doomed to fail obviously at gigabit. But
>they're cheap. For 40 euro i see several getting offered already.
>First important question is of course how much system time those NIC's eat
>when fully loading their bandwidth.
>Example, i have an old dual k7 here with pci 2.2 (32 bits 33Mhz).
>Suppose i put a gigabit card in it.
>In say 6 messages a second i ship 8MB data at a time. Ship and send in turn.
>So it ships a packet of 8MB, then receives a packet of 8MB.
>Other than the cost of the thread to store the packet to RAM, does such a
>card in any way stop or block the cpu's which are 100% loaded with
>searching software (my chessprogram diep in this case)?
>What penalty other than that thread handling the message is there in terms
>of system time reduction to the 2 processes searching?
>Oh btw, i assume that gigabit can handle 48MB/s user data a second?
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Glen E. Gardner, Jr.
Glen.Gardner at verizon.net


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