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

[Yevgeny Kliteynik]

Hi Nicolas,

Nicolas Morey Chaisemartin wrote:
> 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.

Fat-tree should create full connectivity as long as there is an up/down
route between ports. Do you get connectivity between these nodes with
up/down routing algorithm?
Try running it with the same root_guid_file.

-- Yevgeny

> Is there any reasons such a behaviour wasn't implemented yet? Should 
> there be one?
> 
> Regards
> 
> Nicolas Morey-Chaisemartin
> 
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