[ofa-general] opensm routing

[Al Chu]

Hey Jeff,

On Wed, 2008-06-11 at 09:43 -0700, Jeff Becker wrote:
> Basically, we have an Altix ICE cluster connected by a pair of hypercube 
> Infiniband fabrics. External to that, we have some Lustre nodes 
> connected into the cluster with Infiniband. Our goal is to keep Lustre 
> traffic separate from compute (MPI) traffic. Ideally, we'd have 2 
> subnets and an IB router between the Lustre fabric and the compute 
> fabric to accomplish this.

I see.  In your environment, the lustre storage servers are on the same
fabric as your compute nodes?

> Barring that, I thought we could use partitions as follows: compute 
> HCA's and switch ports are on both partitions with full membership in 
> compute partition, and limited membership in I/O partition.  The Lustre 
> nodes and switches would only be in the I/O partition  (full 
> membership). That way, inter compute node (MPI) traffic would be 
> disallowed from using routes through the I/O fabric (by partition 
> membership), and I/O traffic could not interfere with compute (via 
> separate partitions). Is this scheme feasible?
> 
> If that's not possible, the next idea is to modify OpenSM to assign 
> large weights to the links between the compute and I/O fabrics, so that 
> the MinHop algorithm would never consider using these links for 
> inter-compute node traffic.

So dedicating (for example) X out of Y uplinks for MPI only and the
remaining uplinks for lustre only?

Al

> Thoughts? Thanks.
> 
> -jeff
> 
> Al Chu wrote:
> > Hey Jeff,
> >
> > Out of my curiosity, are you just trying to change the routing to
> > improve job performance?  i.e. lustre nodes get special routing vs.
> > compute nodes?
> >
> > Al
> >
> > On Tue, 2008-06-10 at 15:08 -0700, Jeff Becker wrote:
> >   
> >> Hi all. I was looking into doing some subnet partitioning to separate 
> >> compute nodes from Lustre nodes, and I saw the following in 
> >> ~sashak/management.git on the OFA server, in opensm/doc/OpenSM_PKey_Mgr.txt
> >>
> >> OpenSM Partition Management
> >> ---------------------------
> >>
> >> Roadmap:
> >> Phase 1 - provide partition management at the EndPort (HCA, Router and Switch
> >>           Port 0) level with no routing affects.
> >> Phase 2 - routing engine should take partitions into account.
> >> ...
> >> Phase 2 functionality:
> >>
> >> The partition policy should be considered during the routing such that
> >> links are associated with particular partition or a set of
> >> partitions. Policy should be enhanced to provide hints for how to do
> >> that (correlating to QoS too). The exact algorithm is TBD.
> >>
> >>
> >> What is the status of Pkey-aware routing? Thanks.
> >>
> >> -jeff
> >>
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> >>
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> >>     
> 
-- 
Albert Chu
chu11 at llnl.gov
925-422-5311
Computer Scientist
High Performance Systems Division
Lawrence Livermore National Laboratory