Failure of software, hardware, or local disk on a reader causes a temporary outage for connected clients.
Clients connected to any other node will continue to function without disruption. Any distributed query being executed on the reader where the reader is not the leader node for that query will be completed by the leader node and thus cause no disruption to clients connected to the rest of the nodes.
Clients connected to the failed reader will see an outage. When the clients try to reconnect, they can be redirected to a node that is up using the login redirection feature or using a third party redirector. Depending on the severity of the failure, the failed node can be restarted if it is a software issue or restarted after fixing the hardware or disk issue.