Replacing Quad proc SMP multi node DEC Alpha Cluster with Linux Dual P4 cluster?

George France france at handhelds.org
Thu Apr 18 13:11:28 EDT 2002


Have you considered a quad processor EV68 (EV7 when they become available) 
Alpha system?  

--George

On Thursday 18 April 2002 09:27, shin at guss.org.uk wrote:
> Hi,
>
> We have an old cluster setup that has 3 Alpha 4100 nodes (each node
> has 4x466 processors) connected with memory channel (first version),
> 1Gb Ram per node. The cluster is used to run internal code which is
> mostly CFD (fine grain synchronous) problems. The code is parallized
> and currently uses dec's mpi implementation.
>
> We now need to replicate this system at a remote site, and with an
> eye on keeping the cost down, so the idea is to go with a bunch of
> dual processor P4 (2GHz xeon?) systems with 2Gb ram each and myrinet
> interconnect.
>
> We expect to want to scale up to at least 8 of these dual nodes
> initially.
>
> I need to look into the performance of various aspects of the
> proposed system as we have no experience in this type of setup.
>
> Disclaimer: I dont' necessarily know what I'm talking about - I'm
> the hardware/admin guy; the parallel guys do all the coding! Sorry.
>
> I'd appreciate any answers anyone could offer on:
>
> 1. In terms of the floating point performance, looking at CFP2000 on
> www.spec.org and the Xeon should offer much better FP performace
> that the older alphas we have. I could only find results for a 4100
> 5/533 (which is the closest to our current setup) and these were
> much lower than the results from Dell Precision Workstation 530 with
> 2.0Ghz proc.
>
> So I assume this won't be an issue - we'll get fast processors. Is
> there a mboard that really sticks out here for offering best support
> to these processors - or should we even be looking at AMD MP systems
> now. I'm not sure I have the timescale to get in test systems and
> test anything out.
>
> 2. Quad systems seem to be way more expensive than duals and I could
> only find quad systems running at 900Mhz per proc instead of 2GHz in
> the duals - so I assume the quads are out on cost and proc. speed
> alone.
>
> 3. One of my concerns was the use of mpi across 8xdual Xeon nodes
> versus 3xquad alpha nodes. I'm assuming that mpi(ch) will look after
> all the necessary for us in terms of communication between
> processors within a node and communication across nodes - but is the
> speed of memory, throughput etc a limiting factor on this type of PC
> architecture? Will we hit latency issues within a node that we're
> not currently hitting?
>
> What sort of memory is recommended? DDR/SDRAM/other?
>
> However having ruled out the quads above - will they offer better
> memory performance than the duals - on a par with the quad alpha
> nodes? (I appreciate it's not a like for like comparison).
>
> 3. I think an entry level myrinet switch will enable me to connect 8
> nodes - at a cost of approx 2400 USD for a switch and 1700 USD per
> myrinet card per node? And it will offer better performance than our
> MC - so I'm assuming that the choice of myrinet is ok.
>
> 4. In terms of cache - we believe that the large cache on the
> alpha's helps our performance quite significantly - as far as I can
> determine the cache on the xeons is still 256/512K? Presumably this
> won't make that much of a difference as we're scaling out across 8
> nodes instead of 3?
>
> Many thanks in advance,
> Rgds
> Shin
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