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I have been using Mellanox ConnectX 2 QDR cards in a point to point link between two machines, with opensm running on one machine. This has worked very well.

Recently I got a Mellanox IS5022 switch - which does not run an SM. So I know I still need that opensm instance running.

If I insert the IS5022 between the two machines, do I need to restart opensm?

My reading says I do not have to. However theory and practice do not always agree ;-)

If inserting the switch will confuse opensm, then I'll schedule that change for off peak hours.

Thanks in advance!

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  • OK, I see I should have asked: "If I insert an Infiniband switch..."
    – Eric M
    May 17 '17 at 4:15
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In short - no, you don't ever have to restart OpenSM.

If you have OpenSM running with "normal" configuration (that is, you didn't tweak it with some parameters to disable some of its capabilities), OpenSM will react to any change in the subnet and will reconfigure whatever is needed.

As a side note: inserting a new switch will involve disconnecting a cable from the HCAs, which means that both HCA's ports will go down, so there isn't really a difference between restarting OpenSM and not restarting it.

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  • Thanks kliteyn! I understand the ports will go down. I was looking for knowledge about the scope of impact of the change.
    – Eric M
    May 17 '17 at 23:41
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    A caveat to be aware of is that opensm scans the network periodically, and new connections don't come up right away. Thus, after you make your change, it may take 15-30 seconds or so for the links to be fully up. In other words, don't worry if your link lights don't come up right away.
    – Paul
    Nov 15 '17 at 21:25

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