[Beowulf] myrinet (scali) or ethernet

Patrick Geoffray patrick at myri.com
Tue Oct 5 08:05:29 EDT 2004


Hi Patricia,

Patricia wrote:
> I am user of two clusters: One runs under myrinet and
> the other under scali. In both cases I installed my

Myrinet is hardware and Scali makes software. Do you run Scali's 
software on Myrinet ?

> jobs are indeed running under myrinet (scali) or
> ethernet.

Do you link with Scali's software or MPICH-GM ? If it's MPICH-GM, 
binaries will only run on Myrinet. If it's Scali, I don't know, I guess 
it chooses Myrinet or Ethernet at runtime. In this case, you can look at 
the output of gm_board_info on a node where your job is running, and see 
if any of the PIDs and the command lines of programs using a GM port 
matches your application process. It may still be possible that Scali 
opens a GM port without using it. Another solution would be to unplug a 
few nodes but Scali may be able to use Ethernet only for the nodes where 
Myrinet has been unplugged. You can also look at the GM counters (with 
gm_counters) and see if the number of packets sent/received goes up. 
However, you would not be sure if another process is using Myrinet at 
that time or if IP/Myrinet is up and running too.

I guess there should be a way with Scali to know which device is used at 
runtime, but I really don't know how.

Is it the same problem than the Myricom Help ticket #30885 ?

Patrick
-- 

Patrick Geoffray
Myricom, Inc.
http://www.myri.com
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