[Beowulf] The move to gigabit - technical questions

Vincent Diepeveen diep at xs4all.nl
Tue Mar 15 15:11:44 EST 2005


At 05:41 PM 3/14/2005 -0500, Glen Gardner wrote:
>Gigabit will be a little faster than 100Mbit on a small cluster, but not 
>a lot.

What is 'not a lot'.

I would guess it's factor 10 faster in bandwidth?

>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.

Very interesting, can you post a connection scheme and routing table?

>It also let me use gigabit network cards in my I/O node and controlling 
>node with a small improvement in file I/O.

Streaming i/o or random access?

cheapo disk arrays get what is it, 400MB/s handsdown or so?

that's raid5 readspeed, plenty security at a raid5 array.

>The compute nodes remaind with 100 Mbit to conserve power. The setup 
>works rather nicely.

what type of software do you run at it,
embarrassingly parallel software?

Vincent

>Glen
>
>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?
>>
>>Vincent
>>
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>>
>
>-- 
>Glen E. Gardner, Jr.
>AA8C
>AMSAT MEMBER 10593
>Glen.Gardner at verizon.net
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>
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