Best way to quickly drain web server connections

Your persistence rule are a factor here, as wlopez indicated, Disable will stop new connections, but it allows active connections to finish up gracefully. The big difference is, the customer experience, usually you would be more concerned about customer experience than waiting for the customers to bleed off. If your connections are stateless, then you should be able to force them offline, with minimal impact to users. Most likely they are state-full connections and you want them to finish up their business, but one factor that might help, is your persistence timeout value.