[ofa-general] opensm: Routing on non-pure Fat-Tree

[Nicolas Morey Chaisemartin]

Hello,

I am conducting some tests on routing non-pure fat-tree network using 
the fat tree algorithm of OpenSM.
The network I am experimenting on is a 3 level fat tree, with a pruned 
3rd layer.
By providing the root_guid_file, the algorithm works great !

The problem is, we would like to add some service nodes directly on the 
3rd level switches.
I have added the cn_guid_file so the network is still recognize as a fat 
tree.
OpenSM once more manage to create the routing for the network. It 
provides full connectivity,
 except there are no routes between non computes nodes.
I understand that the point of setting these node as not compute node 
should intend they won't talk to each other, but we still need a bit of 
connectivity between them to exchange few datas (pings and such).
A simple min-hop or such should be enough to generate those routes.
It will probably desequilibrate the number of routes going through the 
top links, but those additional link makes virtually no traffic at all, 
so in practical it shouldn't be a problem.

Is there any reasons such a behaviour wasn't implemented yet? Should 
there be one?

Regards

Nicolas Morey-Chaisemartin