[Beowulf] 48-Core X86_64 Compute Node - Good Idea?

Mark Hahn hahn at mcmaster.ca
Mon Jun 14 10:29:15 PDT 2010

> right now, I believe such boxes aren't available
> yet. The closest thing is a 4-way 1U box, which
> gives 48 cores per rack unit, but in *1 node*.

well, the supermicro website lists them:

> My intuition tells me that I should be wary of
> such a configuration because of various SMP-related
> locking and concurrency issues.

why?  is there something peculiar about your workload, and especially
something that would show up with modestly higher SMPness?

> There probably aren't
> many single node 48 core boxes out there so there
> might be surprises. I don't like surprises.

this is hardly uncharted territory.  SGI's been there forever,
and some fringe boxes from Intel.  but 8s 4c has been pretty mundane
for a while, and doesn't need any sort of hand-holding.  unless you
mean something like "I expect to swap a lot and want to configure 
a single non-raid swap partition", I don't really see what you're 
worrying about...

> The obvious thing to do would be to wait until
> the Twin boxes come out but my problem is that
> I have money to spend that has to be spent soon,
> maybe before the Twin boxes come out. So, I'm trying
> to decide what to do. (I only want 1U boxes because
> I have to pay for rack space).

I think people should actually take fresh look at 4s 1U boxes
because AMD has eliminated the "4-socket penalty".  there are some 
nontrivial advantages to fatter nodes - they let you achieve some
unique workload configurations (bigger memory, higher-threaded, etc).
sysadmin work doesn't scale linearly as the number of nodes, of course,
but having fewer, fatter nodes can be attractive TCO-wise, too.

regards, mark hahn.

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