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DLC September 10, 2010 19:12

looking for needed
Hello everyone,
I'm interested in running cfd simulations around sailing boat hulls and sails with OpenFoam.
I was thinking to buy some hardware but I have no Idea of which is the price of multi processor PC or small clusters.

I imagine that I will need at least 16 processors...

can anyone give me any suggestions and Ideas?



andyj September 17, 2010 07:27

I suggest starting out with one single quad core computer, running a Linux server operating system. Examples of Linux server software are: Scientific Linux (Cern & Fermilab, Red Hat Enterprise-modified) or Centos or Red Hat Enterprise-you can buy support, or other free open source linux server software. Maybe buy Sun Solaris. If it has to be a Windows system, maybe Windows Home Server , or Windows Server.

The advantage of using server software is so you can expand to more than one computer using a Linux Cluster configuration to allow parallel computing, if one computer will not provide eneough computing power for your needs. Scientific Linux is configurable for cluster setups, as are other distros.

One computer might be eneough, maybe not..try just one first.
64 bit Operating systems can handle larger amounts of motherboard memory. I would suggest at least 4 Gb . Use a full sized ATX motherboard, as mATX boards usually do not have enough ram slots. 600 watt power supply. Use a new power supply as used ones cause unspecified problems and they dont go bad all at once. SATA hard drives are very fast, 7200 rpm reccomended, 10,000 rpm is better.

I would simply build the computer yourself. And install the operating system yourself. You can build one with new parts for under $200 if you shop wisely and use Linux.

The only difficult part is installing the cpu into the motherboard, as the processors have 940 little pins that go down into the motherboard and you can not bend a single one..but its actually easy if you follow the directions. You do not use much force to seat the cpu into the motherboard, correctly position it and use a light tap with a finger ( think the amount of force you would use to move a full 12 oz can of pop one inch with your finger on a smooth desk.. zero force..) Buy a boxed cpu unit with a factory fan. Put thermal paste (as thick as a piece of paper) on the cpu before seating the fan on the cpu. Configure the bios correctly ( ) There are tutorials on Youtube on how to build a machine. You might need a book on Linux if you are not familiar with it, and maybe pay a local Linux guru to help cofigure the OS.

Use the hardware that is compatible with your version of linux (ethernet cards can cause kernal panic problems with the wrong drivers) .

You may find a single quad core to be more than adequate.

If not, then add a second quad core or more. You could also use a dual core or single core. You would want at an absolute minimum an single core Athlon with 512k L2 memory on the cpu. But you really should start out with a quad core or dual core from the start. AMD Quad cpu model 640 Phenoms and AM3 motherboard combo can be found new for $100 US dollars for both the motherboard and cpu!! Intel makes a great quad cpus , but its about $300 more to build an Intel system.

For cpu capabilities, see:
nice color charts!
The problem with any quad core is cooling. Cool the case first!.. You need to have case cooling fans..120mm preferred or at least 80mm. I use a passively cooled Asus Radeon HD 3450 with 512 mb ram for a video card. The heat sink is huge and the cpu never overheats, even when left running all day. They are not very expensive...maybe $35 max. ...the reason for 512 mb or larger Video card memory, is a large mesh or CAD file can bring a video card to standstill if it does not have eneough onboard ram. A very fast expensive card would probably be used for watching real time chemical reactions or something similar, or a large data set.

I am not sure how complex your model is, and cant tell you how many processors to buy, but starting with one and buying more if needed makes sense to me.

I have a dual boot Quad AMD Phenom 9950, 4gb ddr2-1066, Windows 7 x64 bit, Scientific Linux x64 bit system. I am going to add 32 bit Linux for a triple boot system next. At idle with openFoam, cpu use is zero . I benchmark my system with pcwizard by cpuid, to confirm correct operation.. its uses it.
Good luck!!!

DLC September 18, 2010 04:30

Hi Andy!
Thanks a lot for your exhaustive answer!
At the moment I am running on a cluster in university, and I usually run simulations from 8 to 64 CPUs.. unfortunately as soon my master thesis ends, I wont have access anymore to that cluster...I was wondering how much would it cost me to buy some equivalent hardware...
Thanks again!

andyj September 18, 2010 19:26

If you could build one computer with the software you use for modeling you could assemble your model and send it to a supercomputer center to be solved. You would have to find a University or Government research lab that would run your model. You need one that uses your modeling software, or load their modeling software on your computer.That is the cheapest way.

Some of the visualizations you see have been done by clusters with over 9000 cpu's!

But I think you can build your own for $200-250 per computer. I have done it many times. You would be able to do quite a bit with four quad core computers.
There are grid arrays which use different type computers for paralell tasks, and there are Linux clusters. Two different methods, Grid vs Cluster. AMD Opteron processors are commonly used in paralell tasks.
It seems like a lot of expense for one indivdual to build a system with over 4-5 computers.
I would find out what software you can use to run your models on and find out who will let you send them your dataset for their supercomputer to run.

There are books on how to build a Linux cluster or Grid:
Linux Enterprise Cluster: Build a Highly Available Cluster with Commodity Hardware and Free Software ISBN-10: 1593270364
Grid Computing, John Josephy, IBM Series Book, ISBN 10-01314456601
good luck!

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