>Because communicating through shared memory when sending messages between processes on the same server is far faster than going through a network stack.
 
I see... But that is not good for diskless clusters. Am I right? assume processes are on a node (which has no disk). In this case, their communication go though network (from computing node to server) then IO and then network again (from server to computing node).

Regards,
Mahmood

From: Jeff Squyres <jsquyres@cisco.com>
To: Mahmood Naderan <nt_mahmood@yahoo.com>; Open MPI Users <users@open-mpi.org>
Sent: Saturday, October 27, 2012 6:19 PM
Subject: Re: [OMPI users] openmpi shared memory feature

On Oct 27, 2012, at 10:49 AM, Mahmood Naderan wrote:

> Why openmpi uses shared memory model?

Because communicating through shared memory when sending messages between processes on the same server is far faster than going through a network stack.

> this can be disabled though by setting "--mca ^sm".
> It seems that by default openmpi uses such feature (shared memory backing files) which is strange.
> 
> Regards,
> Mahmood
> _______________________________________________
> users mailing list
> users@open-mpi.org
> http://www.open-mpi.org/mailman/listinfo.cgi/users


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