[Beowulf] Newbie question.

Ryan Sweet rsweet at aoes.com
Fri Oct 29 02:18:59 PDT 2004

On Thu, 28 Oct 2004, Currit, Dennis wrote:

> We are thinking of putting up a cluster to run MSC Nastran and have about
> $25,000 budgeted for hardware.

Have you also discussed licensing with MSC?  It may have 
changed recently, as my experience here is a few months 
old, but Distributed Parallel features are licensed differently than the 
SMP Parallel features, and are significantly more expensive.

> Is this enough to get get started?

Certainly it is enough to buy a few nodes, but also if you are just 
getting started with clustering it may be good to think a couple of times 
about the direction you want to go and to analyse the associated costs of 
things like additional power consumption, air-conditioning, etc....  If you 
already have a sufficient server room infrastructure (racks, power, ac) 
then perhaps this isn't much of a consideration.

> Any suggestions as to what I should buy?

We are currently running NASTRAN with success on opteron, though we have 
also had good experience with PIV and Athlon MPs.  I think the best thing 
to do is to try and benchmark your actual jobs on a few different systems 
if you can.

> Currently we are running large jobs on
> an older AIX multiprocessor system and smaller jobs on a Xeon 2.8 system, so
> I think even a small cluster should be an improvement.

It depends upon the jobs that you are running.  If your jobs do benefit 
well from running in SMP on the AIX system, then you may also have good 
efficiency with DMP on a cluster.  We have had mixed results with our 
structural analyses: some had near linear speedups on smallish (<16 cpus) 
cluster runs, and others would gain only about 20% for each cpu added.

For many of our NASTRAN runs high speed disk IO is nearly as important as 
as the CPU.  Find out what your job mix is like, and then spend your money 
accordingly (you may want to splash on fast SATA local disks for scratch 
space, or on more RAM to use RAM disks for scratch).

Also have the engineers read through the manual regarding the DMP options 
because you have to pay a bit more attention to how your jobs are 
configured when using distributed parallel.

good luck,

Ryan Sweet             <ryan.sweet at aoes.com> 
Advanced Operations and Engineering Services
AOES Group BV            http://www.aoes.com
Phone +31(0)71 5795521  Fax +31(0)71572 1277

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