Fabric Manager Users Guide, Version 6.1, Revision A - QLogic

2–Advanced Fabric Manager Capabilities
Fabric Unicast Routing
The QLogic Performance Scaled Messaging (PSM) layer can take advantage of
LMC to provide dispersive routing and load balance MPI across multiple routes.
See the QLogic OFED+ Host Software User Guide for more information about
PSM's dispersive routing capabilities.
When LMC is configured with a non-zero value, the SM assigns routes with the
following goals in priority order:
1. Each LID for a given destination port is given as unique a route as possible
through the fabric, using completely different switches when possible or at
least different ports in the same switch. This approach provides optimal
resiliency so that fabric disruptions can be recovered from using APM and
other rapid failover techniques.
2. The overall assignment of Base LIDs to ISLs is statically balanced, such that
applications which only use the Base LID will see balanced use of the fabric
3. The assignment of LIDs to ISLs is statically balanced, such that applications
which use multiple LIDs for load balancing will see additional available
bandwidth.
PathRecord Path Selection
When a non-zero LMC value is used, the SM will have multiple paths available
between pairs of nodes. The QLogic Fabric Manager permits configuration of the
SM to specify which combinations of paths should be returned and in what order.
Most multi-path applications will use the paths in the order given, so the first few
returned will typically be used for various failover and dispersive routing
techniques.
Most applications will use the first path or only the first few paths. When LMC!=0,
there can be N=(1