[ofa-general] Re: multiple independent IB fabrics connected to the same node

[Or Gerlitz]

On 5/29/07, Bob Kossey <bob.kossey at hp.com> wrote:
>
> Another related question.  Does OFED 1.2 now support multiple
> independent IB fabrics
> (multiple SMs, etc) connected to multiple HCAs on the same node?  Are
> there any
> qualifications about which dimensions are supported with this, such as
> ipoib HA, SRP HA,
> other types of failover, etc.?
>

Hi Bob,

Generally speaking, as far as i am aware, by design the openib stack
--does-- support such a configuration but it must be validated, I cc the
maintainer here, in case they see something that they think is broken under
such a config.

However, note that such a config is somehow problematic (broken) for High
Availability, specifically looking on IPoIB HA, say you have two nodes, n1
and  n2 connected to two subnet S1 and S2 and now the n1/S1 link is broken
and bonding does fail over to the IPoIB interface on S2 such that n1/S2 is
the active link. At this point, for n2 to commuinicate with n1 it --must--
failover also to S2, when it would not have to do so if S1 and S2 were the
same fabric.

This is only a simple (non) use case to examplify the problem here. My take
on that you better avoid rely on HA between subnets using tools like
bonding. If you use higher level HA tools it --might-- make sense to plan
for using two independent subnets.

Or.
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