User Manual

Features Overview and ConfigurationRev 2.3-1.0.1
Mellanox Technologies
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The following rule is equivalent to how OpenSM used to run prior to the partition manager:
Default=0x7fff,ipoib:ALL=full;
3.2.2.4 Effect of Topology Changes
If a link is added or removed, OpenSM may not recalculate the routes that do not have to change.
A route has to change if the port is no longer UP or no longer the MinHop.
When routing changes
are performed, the same algorithm for balancing the routes is invoked.
In the case of using the file based routing, any topology changes are currently ignored. The 'file'
routing engine just loads the LFT
s from the file specified, with no reaction to real topology.
Obviously, this will not be able to recheck LIDs (by GUID) for disconnected nodes, and LFTs
for non-existent switches will be skipped. Multicast is not affected by 'file' routing engine (this
uses min hop tables).
3.2.2.5 Routing Algorithms
OpenSM offers the following routing engines:
1. “Min Hop Algorithm”
Based on the minimum hops to each node where the path length is optimized.
2. “UPDN Algorithm”
Based on the minimum hops to each node, but it is constrained to ranking rules. This algorithm
should be chosen if the subnet is not a pure Fat
Tree, and a deadlock may occur due to a loop in
the subnet.
3. “Fat-tree Routing Algorithm”
This algorithm optimizes routing for a congestion-free “shift” communication pattern. It should
be chosen if a subnet is a symmetrical Fat
Tree of various types, not just a K-ary-N-Tree: non-
constant K, not fully staffed, and for any CBB ratio. Similar to UPDN, Fat Tree routing is con-
strained to ranking rules.
4. “LASH Routing Algorithm”
Uses InfiniBand virtual layers (SL) to provide deadlock-free shortest-path routing while also
distributing the paths between layers. LASH is an alternative deadlock-free, topology-agnostic
routing algorithm to the non-minimal UPDN algorithm. It avoids the use of a potentially con-
gested root node.
5. “DOR Routing Algorithm”
Based on the Min Hop algorithm, but avoids port equalization except for redundant links
between the same two switches.
This provides deadlock free routes for hypercubes when the
fabric is cabled as a hypercube and for meshes when cabled as a mesh.
6. “Torus-2QoS Routing Algorithm”
Based on the DOR Unicast routing algorithm specialized for 2D/3D torus topologies. Torus-
2QoS provides deadlock-free routing while supporting two quality of service (QoS) levels.
Additionally
, it can route around multiple failed fabric links or a single failed fabric switch
without introducing deadlocks, and without changing path SLvalues granted before the failure.
mgid=ff12::1,sl=1,Q_Key=0xDEADBEEF,rate=3,mtu=2 # random group
ALL=full;