Yes, but during a change window. When the patch installs on each node, that node will be down during the install.
So you need to plan for outage of nodes. If you only have one node, then it would result in an authentication outage. If you have two or more nodes, the list is the NAD will mark the second radius server down and authentication will continue. It relies on proper NAD config.
Patch 9 is safe to install, I know many deployments on it, but it's always reccomended to do a bug scub.
