[Beowulf] Low cost Hi Density - Nehalem clusters

[amjad ali]

Hi,
while looking for high density (fat) nodes; one should keep in mind that
more number of cores striving simultaneously to access memory, cause memory
contention. Infact today CPU cores are fast and scalable but not the memory
bandwidth. Experts say that buying a CPU is infact buying "bandwidth" not
the "speed".

Intel's specialty is QPI (quick path interconnect) --- removed Front Side
Bus (FSB), in Nehalem CPUs, as an effort to over come the bottleneck of
memory bandwidth. This bottleneck arises when more number of cpu cores, each
performing floating point oprations in HPC applications, strive to get
access to main memory simultaneously. Also Intel introduced QPI to compete
with the AMD's speciality Direct Connect Architecture (DCA) in its latest
CPUs.

Nehalem Xeon 55xx are "server" class while Nehalem Core i7/i9 are "desktop"
class cpus.

In server processors
Today in Servers latest (Nehalem) Quad core Xeon 55xx (DP/ for dual socket
boards) and Xeon 35xx ( UP/ for single socket boards) are alive.
Today in Servers Quad core Xeon 54xx (DP/ for dual socket boards) are not so
good.
And Xeon 53xx (DP/ for dual socket boards) are virtually dead.
And Xeon 33xx/32xx ( UP/ for single socket boards) are not so good.

Today in Servers latest Quad core and Six Core Opteron 83xx and 84xx
(Shanghai -- 3rd generation) are alive.
Today in Servers Opterons 13xx/23xx/24xx (Budapest/Barcelona --- 2nd
generation) are not so good.

There price differences reflect these 'facts'.


On Tue, Nov 24, 2009 at 10:41 PM, Jon Forrest <jlforrest at berkeley.edu>wrote:

> Ralph Mason wrote:
>
>> We have been building a development cluster using consumer core i7
>> processors with 12gb of ram each and a ide cf boot disk on a motherboard
>> with embedded everything.  This is very cost effective as it uses consumer
>> processors and the cheapest ram (ram prices skyrocket once you go higher
>> than 2gb modules).
>> Does anyone know of any commercial offering that can pack these nodes into
>> a high density rack or offer a similar price performance curve for the given
>> ram and processing power?
>>
>
> I've recently used Finetec (www.finetec.com) to put together
> a cluster based on the dual-motherboard Supermicro cases.
> Since each motherboard can hold 2 processors, and each AMD
> Istanbul processor has 6-cores, I can get 24 cores per rack
> unit. That's pretty dense.
>
> I believe that SuperMicro also makes similar motherboards
> for Intel processors.
>
> Check it out!
>
> Cordially,
> --
> Jon Forrest
> Research Computing Support
> College of Chemistry
> 173 Tan Hall
> University of California Berkeley
> Berkeley, CA
> 94720-1460
> 510-643-1032
> jlforrest at berkeley.edu
>
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