[Beowulf] recommendations for cluster upgrades

Jan Heichler jan.heichler at gmx.net
Tue May 12 23:55:40 PDT 2009

Hallo Mark,

Mittwoch, 13. Mai 2009, meintest Du:

>> I'm currently shopping around for a cluster-expansion and was shopping
>> for options. Anybody out here who's bought new hardware in the  recent
>> past? Any suggestions? Any horror stories?

MH> I think the answer depends on time-frame.  if you're bw-sensitive,
MH> you go nehalem for the time being.  

I'm really surprised that everyone just screams "Nehalem" - of course the platorm is the fastest that you can buy for money at the moment. It is the youngest design so that is not suprising. 

But clustering is always about price/performance. And AMD doesn't look so bad there. Shanghai-pricing was lowered in February and another pricedrop is expected when Istanbul is launched. So Nehalem is faster but more expensive. For some Applications it is "more expensive" than it is "faster".

Memory, CPUs and Chipsets for Intel are expensive - what you can buy from AMD is "old" hardware that is in the market now for quite some time. It is simply cheaper. 

The 2.4..2.6 GHz Shangais are interesting. 

MH> for the near future, I'm interested to see how AMD's next-gen "istanbul" works out.  

It seems to be very interesting. 

When Clovertown/Harpertown was launched by INtel it seemed like they designed the CPU just for getting to the top500. High HPL-scores but other applications did not always perform good. Istanbul seems to be the perfect top500-CPU. You reach a high Number of cores in a small power footprint. HPL-efficiency is very good. Let's see how real applications behave ... what i've seen so far was looking interesting enough!

MH> AMD obviously needs 
MH> to break out past ddr2/800 - it would be kind of surprising if they 

They will ... but having a stable platform was also important. And AMD kept the socket-F now for quite some time.

MH> went 6c/socket without some improvement.  AMD has made a big deal 
MH> about the cache snooping, but I'm not sure how much it matters for 
MH> the main market (2-socket).  

You have two things: 

HyperTransport3 - some Shanghai have it (the really fast ones with the odd product numbers). And of course all Istanbuls. It enables them to handle a lot more coherency-trafic. But in a 2-way mainboard it is not a big performance impact.
HT-Assist	- some kinde of snoop filter for Istanbul. Without this Istanbul probably wouldn't scale to 6cores at all. But real world performance seem to be interesting... so HT-Assist seem to make a difference.

MH> if you're considering 4-socket, I'd 
MH> certainly think about whether to wait for istanbul.

Istanbul or at least Shanghais with HyperTransport3 - it makes a much bigger difference there...

>> We've been using Dell SC1435's with Quad-Core AMD 2354 Opterons @
>> 2.2GHz. 16 Gig RAM.

MH> 2G/core seems to be fairly safe.  although it's overkill for a lot of 
MH> users, ram is also pretty cheap - 6x 4G dimms for dual-i7 is probably
MH> pretty sensible.

12 x 2 for E-Series Xeons or 6 x 4 for X-Series Xeons.... but that is another thing with Nehalem: you have to buy 50% more RAM (if you are just looking for 2GB/Core) to get good performance. Same is true for Istanbul... the metrics are changeing ;-)

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