[Beowulf] Virginia Tech upgrade

Mark Hahn hahn at physics.mcmaster.ca
Tue Jan 27 21:09:33 EST 2004

I draw several conclusions from the VT cluster:

	- HPL is very cache-friendly.  the dual-G5 has an impressive peak
	flops rating, but pretty mediocre memory bandwidth.  anyone have a 
	Stream result for a G5?  I'd guess around 2.5 GB/s.

	- HPL also doesn't penalize fractional bisection bandwidth clusters,
	which is pretty interesting, since it *does* seem to reward
	post-gigabit interconnect.  latency, perhaps?

	- the press isn't smart enough to notice that the VT cluster was 
	far too unreliable (no ECC) and used an aweful lot of floorspace.
	it *is* neat that clusters are commodities nowadays, but is that news?
	somehow I don't think very many future clusters will be built by 
	pizza-motivated volunteers...

	- a good PR stunt buys a lot of vendor discount.  remember: the G5s
	list at close to $5M total, and the IB kit is pushing $2M.  I'm
	guessing that VT can sell the G5's at a 30% discount.  and Xserves cost
	about 50% more than desktops, so VT winds up with around $10M from 
	Apple, for around $3M investment, nice!

> The xserve has ECC memory, which will bring the performance of their cluster
> up to what they say it is.

oh, come on.  MTBF is ~10 hours, so short jobs are perfectly fine ;)

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