[slurm-users] Question about using topology/tree

[Antonio Lara]

Hello,

I'm trying to use the topology/tree plugin to isolate nodes in different 
"groups", so that jobs can be allocated only on nodes belonging to one 
such group, and not in nodes from other groups. I think I'm missing 
something, because Slurm doesn't seem to take this topology into 
consideration. Hopefully someone can spot what I'm doing wrong. So far 
I'm trying to separate a 3 node cluster into two groups, using two 
switches. I have created a topology.conf file, and placed it in the etc 
directory of the slurm installation path. This file contains these two 
lines:

SwitchName=s0 Nodes=node1,node2
SwitchName=s1 Nodes=node3

I also tried adding a third switch that contains the s0 and s1 switches, 
but it didn't solve anything.

Then, I have enabled the use of the topology/tree plugin with this line 
in slurm.conf:

TopologyPlugin=topology/tree

And finally these changes are taken into consideration with:

scontrol reconfigure

Then, I would expect that launching a job that requires 2 nodes would be 
run on node1 and node2 only, since these two shoud be grouped under the 
switch "s0", but it runs on node1 and node3, ignoring the topology, when 
I send a command like this:

sbatch -A molecules_serv -p cc -N 2 -n 4 --switches=1 ./script1

Maybe I'm not understanding correctly what the --switches flag does, but 
I think it should only consider nodes that are under 1 switch, and among 
those, use those that can at the same time fullfill the other 
requirements, like the number of nodes or tasks. Therefore I would 
expect it to only run the job in node1 and node2 in parallel, but not 
node3.

Any ideas?

Thank you very much for your help

Antonio