Leo,  Yes.  What that will do is prevent new connections from being handed out to clients.  This won't disconnect any clients already on the node so it's safe.  THat being said, most SMB connections are long lived so it may not help that much.  If you do want the least disruption, I would suspend the node from SmartConnect as early as possible.  That way you hope that as clients disconnect and reconnect there will be fewer connections on that particular node so the disruption will be minimized.
Ok....having a brain *smoke-event*...(i'd insert bad words here but it wouldn't be nice!).....  For a repair replacement of hardware on a node - best practice would be to *suspend* operations and shut down just that node using the follow command?:  isi networks modify pool --name : --sc-suspend-node    ...I just cant think today....and never had to replace anything while its operational.  Thanks!!  __LEO__   
Suspend node for hardware maintenance ISILON - OneFS 7.0.2.5