[ofa-general] OFED Roll

[Doug Ledford]

On Mon, 2008-10-06 at 11:57 -0400, publications wrote:
> Am I correct that the Cisco OFED Roll installs Infiniband but not Infiniband
> over IP?  Does it just use RDMA as a transport?

You have your acronym reversed in your mind.  There is no such thing as
Infiniband over IP, it's IP over IB (IPoIB).

> The OFED download from Openfabrics installs IB over IP and I prefer not to
> use it since the latencies are double that of RDMA and the throughput is
> about one half of RDMA.

The presence of IPoIB doesn't not slow down native IB communications.
You're right that it's half the improvement of actual RDMA, but that's
because it's only there to allow IP based apps to run over IB unchanged.
If you write your app to use RDMA, then it uses RDMA and gets the full
benefit of RDMA regardless of any other apps using IPoIB.

> So, another question.  Suppose I have already installed OFED 1.3.1 with IB
> over IP.  How do I configure my system (including the ib0.conf and other
> conf files) to use RDMA rather than IB over IP?

See above.  You have nothing to do.  It's properly configured as it is.

> Thanks for your help.
> 
> Jim
> 
> 
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-- 
Doug Ledford <dledford at redhat.com>
              GPG KeyID: CFBFF194
              http://people.redhat.com/dledford

Infiniband specific RPMs available at
              http://people.redhat.com/dledford/Infiniband

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