[Beowulf] Begginers question # 1

Joshua mora acosta joshua_mora at usa.net
Wed Oct 6 21:06:35 EDT 2010


Hi Gabriel.
If your app is something single threaded (ie. runs on single core) that works
on a per frame basis and it is fairly cache friendly, then the more cores the
better from ecconomical point of view without hurting necessarily on
performance. A fat node would do as well as a bunch of tiny nodes but it will
save you for sure a good chunk of money on interconnect and maintenance
headaches. Power consumption wise will be also better (more efficient usage of
electricity).
A fat node will agglomerate linearly the computing power of tiny nodes. Again
under the assumption of single threaded apps running concurrently and
_being_cache_friendly_.
Also you do not need in that case a high speed interconnect with low latency
since processes are not "talking" to each other. If you got a lot of data to
transfer in and out of the nodes , then 10Gigabit may increase your
productivity from the point of view of getting data in and out of the nodes
faster, but it better be that part about 20% of the whole thing to really
compensate the cost and shrinking that portion only significantly. You may
also want to have fast local file system since all cores are
dumping(reading/writing) the processed frames more or less concurrently.
Number of cores per memory controller is something you want to look at when
running your app in "rate" or embarrasingly parallel mode in order to figure
out if you are running out of bw. Do not confuse it with memory capacity,
which you will need proportionally to the number of cores plus a bunch of it
for file system buffers to accelerate the File I/O.

Hope it helps to start defining your rendering farm.

Regards,
Joshua




------ Original Message ------
Received: 01:03 PM CDT, 10/06/2010
From: gabriel lorenzo <macglobalus at yahoo.com>
To: beowulf at beowulf.org
Subject: Re: [Beowulf] Begginers question # 1

> First of all thanks to everyone who have answered my question. The goal is a
rendering farm. An 8 node prototype would be the star point but eventually a
40 node unit # 1 ( rack ) is the actual project. 
> thanks
> d.g.i gabriel o lorenzo
> 
> 
> 
> 
> 
> Message: 1
> Date: Mon, 4 Oct 2010 16:12:20 -0400
> From: Michael Di Domenico <mdidomenico4 at gmail.com>
> Subject: Re: [Beowulf] Begginers question # 1
> To: beowulf at beowulf.org
> Message-ID:
>     <AANLkTi=JXGx1DohbFMGH-CzuftXiPw4gAS7QEh-ZGP-v at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> To answer your question directly, the answer is, no the performance is
> not the same.  BUT, you've asked a very workload dependent question,
> but have not told us anything about what you're trying to do, so
> deciding which is the right choice is pretty hard.  It would be unwise
> to make this decision solely on price, without understanding the trade
> offs in productivit
> 
> 
>       
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