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Alexei Popov
alexei.a.popov@gmail.com

it seems you are using the benchmark that is simply
too small for your cluster. If you look here,
you'll find that it takes ca. 400-500 seconds to complete on 8 cores.

Actually, with the latest processors Firefly seems to need the
updated set of benchmarks, at least for parallel runs.

I'd suggest you to test performance and scalability of your
particular cluster/setup using job that takes at least 1-2 hours
to complete on 8 cores running on single node.

Your nodes are fast, and my guess is you are using 1 Gbit Ethernet?
This is most likely optimal solution for such a small cluster,
at least the price/performance ratio is very reasonable.
However, you need high quality Ethernet adapters and really
good switch. Formally you need 8-port switch but I doubt
if a typical 8-port switch will be good enough for your purposes -
so you can try to experiment with 16 or 24-port models.

regards,
Alexei





On Tue Mar 30 '10 1:45pm, Vyacheslav wrote
------------------------------------------
>Hi!
>Alex, we used your options for tests without appreciable improvement. We have destroyed our cluster, reinstall OS on all nodes and have again created the cluster – results are the same…
>Below I apply some results for MP2 input, taken from Performance page (in %):

>Cores     xdlb=t     bind=t   blkdlb=0      nbiolb=1         sndbuf=256_rcvbuf=256

>8         100          100        100              100                     100
>16        166.7      178.7     165.4         169.6                  176.3
>24        127.4      121.8     121.8         127.6                  124.1
>32        182.4      165.4     181.1         186.1                  194.2
>40                                                                                  194.2

>Options p2p=.t.  xdlb=.t. are presented in all inputs. Influence of sndbuf and rcvbuf values variation from 64 up to 1024 is insignificant.
>Have you any ideas? We haven't. Unfortunately, we have no any IT expert - both of us only chemists.

>Sorry, I've overlooked to mention, our HPC version is intended for Server 2008 Standard, not for Server 2008 R2.

>------------------------------------------------------------------------
>On Sat Mar 27 '10 10:08pm, Alex Granovsky wrote
>-----------------------------------------------
>>Hi,

>>sorry for the delayed reply.

>>It your HPC solution is based on Win2K8 R2, (note not R1),
>>you may be affected by the same core parking problem, as Windows 7 users.

> Note we do not test it under Win2K8 R2...

>>Second, just adding

>>

 $p2p p2p=.t. $end

>>does not automatically enables dynamic load balancing. Use at least

>>

 $p2p p2p=.t. dlb=.t. $end

>>or

>>

 $p2p p2p=.t. xdlb=.t. $end

>>You can also give a try to more advanced communication-related p2p options like:

>>

 $p2p 
     p2p=.t. xdlb=.t. 

! to bind to interface 
     bind=.t. 
! to use non-blocked I/O for DLB 
     blkdlb=0 
! to use polling instead of blocking waiting for DLB event
     nbiolb=1 
! to set larger TCP window sizes (in Kbytes) 
! for send and receive buffers.
     sndbuf=256 rcvbuf=256
 $end                          

>>Finally, use "-daf 2" command line option to reduce communication's
>>overhead.

>>regards,
>>Alex Granovsky
>
>
>