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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.
http://www.open-mpi.org/faq/?category=openfabrics#ofa-set-subnet-id

> 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
error
and handle it. If APM is enabled, Open MPI will try to migrate to other
path , otherway we will fail.

Pasha.