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Subject: Re: [OMPI devel] Multi-rail on openib
From: Pavel Shamis (Pasha) (pashash_at_[hidden])
Date: 2009-06-14 15:17:54

Nifty Tom Mitchell wrote:
> On Tue, Jun 09, 2009 at 04:33:51PM +0300, Pavel Shamis (Pasha) wrote:
>>> Open MPI currently needs to have connected fabrics, but maybe that's
>>> something we will like to change in the future, having two separate
>>> rails. (Btw Pasha, will your current work enable this ?)
>> I do not completely understand what do you mean here under two separate
>> rails ...
>> Already today you may connect each port to different subnet, and ports
>> in the same
>> subnet may talk to each other.
> Subnet? (subnet .vs. fabric)
About subnet id definition you may read here.

> Does this imply tcp/ip
> What IB protocols are involved and
> Is there any agent that notices the disconnect and will trigger the switch?
In Open MPI we use RC (connected) protocol. On connection failure we get
and handle it. If APM is enabled, Open MPI will try to migrate to other
path , otherway we will fail.